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Full text of "Genetic and environmental factors affecting performance of three Holstein herds in Colombia"

GENETIC AND EN¥iR■ON^4ENTAL FACTORS 
AFFECTING PERFORMANCE OF THREE HOLSTEiN 
h_ ' HERDS IN COLOMBiA 



By 

JUAN JOSE SAT.AZAR C. 



A DISSEICrAllON PSESENTi'D TO TJIE CRADUATli COUNat OF 

THE UNIVERSITY OF FLORIDA 

IN PARTIAL .FULFILLMENT OF THE REQUIREMENTS FOR THE 

DEGREE OF DOCTOR OF PHILOSOPHY 



^ 



UNIVERSnY OF FI.ORIDA 
1970 



J 



ACKNOWLEDGEMENTS 

I wish to express sincere appreciation to Dr, M. Koger for his 
friendly and personal counsel throughout my graduate program, as 
well as for his helpful suggestions during the preparation of this 
manuscript, 

1 am pleased to extend my sincere gratitude to Dr, C, J, Wilcox 
for his lasting patience and understanding in planning, directing, 
and assisting in the research upon which this study is based, and 
for his guidance during the preparation of this dissertation. 

Grateful acknowledgement is expressed to Dr. A. C. Warnick for 
his helpful suggestions for improving the content and structure of 
this research. Recognition is due to the other members of the super- 
visory committee. Dr. T, J. Cunha and Dr, P. L, Pfahler, 

An expression of appreciation is due to Mr, Omar Verde for his 
fine friendship and generous sharing of time and talent throughout 
the progress of this study. 

Appreciation is deeply extended to Dr. F. G, Martin and Miss 
Sara Harr for their assistance in the statistical analysis. Special 
thanks to Dr. E. Huertas and Dr. A, Ortega for their help in the 
collection of data. Thanks and appreciation are also due to Mrs, L, 
Ingenlath for typing this dissertation. 

Acknowledgement is extended to Instituto Colombiano Agrogecuario 
and to the Rockefeller Foundation for giving financial support to 
pursue this graduate program. 



Bc n a iiV 'i» wiirM «-> Wi— at— tio wi , i 



I am deeply reminded at this time of the memory of my parents, 
who always instilled within me the desire for knowledge. The con- 
tinuous devotion and understanding of my wife, Lucy, during the 
entire period of graduate study, and the inspiration of my daughter, 
Monica, were a source of encouragement. To them this work is 
dedicated. 



J 



I I i 



TABLE OF CONTENTS 

Page 

ACKNOWLEDGEMENTS i ( 

LIST OF TABLES vi 

ABSTRACT 

INTRODUCTION j 

REVIEW OF LITERATURE ,. . 3 

Reproduction 3 

Calving Interva'l 3 

Calving Date to First Heat ....,,..,. 7 

First Heat to First Service ]] 

First Service to Conception , . n 

Services per Conception ]2 

Gestation Length ]^. 

Birth Weight 21 

Reasons for Disposal 28' 

Sex Ratio and Tv;inning Rate 29 

Production , jq 

Year of Calving 3] 

Month of Calving 32 

Age at Calving ^[^ 

Length of Record , . 35 

Days Open . . . , , 37 

Previous Dry Period 39 

Heritability , 4] 

Repeatability k3 

Herd by Sire Interaction L^li 



MATCpiA! c AMn uCTijAnc 



H~ vJ I W^iJ 



hS 



Description of the Herds /49 

Data , 52 

Statistical Procedures , , , 5^ 

Reproduction data ...,..,...,. ^k 

Production data 57 

RESULTS AND DISCUSSION 67 

Calving Interval . , . , , 57 



IV 



Page 

Calving Date to First Heat 70 

First Heat to Fi rst Service /If 

First Service to Conception 76 

Services per Conception 78 

Gestation Length ^ 82 

Birth Weight ...... 85 

^ Reasons for Disposal 88 

J Sex Ratio and Twinning Rate 92 

Production 93 

Year and Month of Calving , 96 

Age at Calving \q-j 

Length of Record ]09 

Days Open ] ]0 

Previous Dry Period ]]] 

Heritability ]\\ 

Repeatability ]]5 

Herd by Sire Interaction , 118 

SUMiMARY AND CONCLUSIONS ] 2i+ 



APPENDIX . . . . 
LITERATURE CITED 



129 
152 



BIOGRAPHICAL SKETCH ]68 



LIST OF TABLES 

J ■'■^'^'^ Page 

'. Situation and climatic conditions of the 

three experimental stations studied 50 



2. Means and standard errors of reproduction 
data 



68 



3. Least-squares analysis of variance for 

calving interval gg 

^. Summary of with in- herd and pooled herita- 

bilities for reproduction data ,.,,.,. 7] 

5. Least-squares analysis of variance for 

calving date to first heat 73 

6. Least-squares analysis of variance for 

first heat to first service 75 

7. Least-squares analysis of variance for 

first service to conception 77 

8. Least-squares analysis of variance for 

service per conception 80 

9. Least-Squares analysis of variance for 

services per conception 81 

10. Least-squares analysis of variance for 

gestation length 84 

11. Least-squares analysis of variance for 

birth weight 86 

12. Summary of reasons for disposal 89 

13. ■ Sex ratio and twinning rate 9^ 

1'-+. Means and standard errors for the dependent 

variables included in production data .... 95 

15. Means and standard errors for the independent 

variables affecting production data ..... 97 



vr 



Page 



milk 



Table 

16. Least-squares analysis of variance for 

yield for first calf heifers 98 

17. Least-squares analysis of variance for fat 

yield for first calf heifers 99 

18. Least-squares analysis of variance for 4% 

fat corrected milk for first calf heifers . , 100 

19. Least-squares analysis of variance for 

milk yield for mature covjs 101 

20. Least-squares analysis of variance for 

fat yield for mature cows 102 



21. Least-squares analysis of variance for 

% fat corrected milk for mature cows .... 103 



1,0/ 



22. Least-squares analysis of variance for 

milk yield for all cows ]0k 

23. Least-squares analysis of variance for 

fat yield for all cows 105 

2^-, Least-squares analysis of variance for 

.4% fat corrected milk for all cows 1 06 

25. Summary of wi thin-herd and pooled herita- 

bilities for production data calculated 

from least-squares analyses .... 112 

26. Analysis of variance for production data 

of all cows adjusted for all significant 

effects except for sire 114 

27. Summary of wi thin-herd and pooled herita- 

bilities for production records of all 

cows estimated from nested analyses II5 

28. Summary of wi thin-herd and pooled repeat- 

abilities estimated from production 

records of all cows 11/ 

29. Summary of herd x sire data , II9 

30. Least-squares analyses of variance components 

and percent of total variance , , 121 

3K Reproduction data card layout I30 

32- Production data card layout. . , , I3I 



VI I 



I ■ 'j; nr i n » B'. i )i«'<<ii ii Bfc.uinwLfc.i 



'' Table .„ 

Page 

33. Means oP the variables studied for re- 
production data by years in Herd 1 132 

3^. Means of the variables studied for re- 
production data by years in Herd 2 I33 

^ 35. Means of the variables studied for re- 

\ production data by years in Herd 3 13!^ 

36. Yearly least-squares coefficients for 

reproduction data of Herd 1 , . , I35 

37. Yearly least-squares coefficients for 

reproduction data of Herd 2 13$ 

38. Yearly least-squares coefficients for 

reproduction data of Herd 3 I37 

39. Mean yields (kg) of first calf heifers 

by years within herds 133 



40, 



Mean yields (kg) of mature cows by 
year within herds 



VI I I 



139 



Mean yields (kg) of all cows by years 

within herds ]iiQ 

^2. Yearly least-squares coefficients for 

production data of first calf heifers , , . . 141 

43. Yearly least-squares coefficients for 

production data of mature cows \k2 

44. Yearly least-squares coefficients for 

production data of all cows ]if3 

^5. Monthly least-squares coefficients for 

production data of first calf heifers .... 144 

46. Monthly least-squares coefficients for 

production data of all cows, , . , 145 

47. Monthly least-squares coefficients for 

production data of mature cows \b^ 

48. Age-correction factors for 305-day 

production records \hn 

49. Rank of sires by herds according to 

their daughters' leasts squares 

means for milk yield ]49 



ggg?ii^rrntTiTwai I w < ■ iMW-uunwia 



H^mg^CMWMBtf 



) 



fable 
51. 



Rank of sires by herds according to their 
daughters' leasts squares means for 
fat yield 



Rank of sires by herds according to their 
daughters' leasts squares means for 
^% FCM 



Page 



150 



151 



IX 



Abstract of Dissertation Presented to the 
Graduate Council of the University of Florida in Partial Fulfillment 
of the Requirements for the Degree of Doctor of Philosophy 

GENETIC AND ENVIRONMENTAL FACTORS AFFECTING 
PERFORmNCE OF THREE HOLSTEIN HERDS IN COLOMBIA 

By 

) Juan Jose Salazar C. 

June, 1970 

Chairman: Dr. Marvin Koger 
Major Department: Animal Science 

Some 2,392 records of three experimental Holstein herds under 

different environmental conditions in Colombia were studied. Data 

included information from 1955-67. Least-squares analyses of variance 

Mere performed for each herd separately. Overall means for the three 

herds were for calving interval 433, 419, and 436 days; for interval 

from calving date to first heat, 86, 63, and 93 days; for first heat 

to first service, 18, 29, and 6 days; for first service to conception, 

61, 60 and 90 days; for gestation length, 280, 279, and 281 days; for 

I birth weight, 38, 36, and 38 kg. The overall number of services per 

1 conception was 2.0. Pooled heri tabi 1 i ties were 0,10 or less for all 

variables except gestation length and birth weight where her i tabi 1 i ties 

i 

1 were 0.28 and 0,22. Major reasons for cow disposal were low reproduc- 

.. -tion and. low production which accounted foi- 41 and 34% of disposals, 
respectively. Approximately 15% of the cows died for different 
causes. From 1,365 calvings studied in the three herds a sex ratio 
of 53% for males, 47% for females, and 1.47% for multip-le births was 
observed. 

Effects of age, length of record, days open, previous dry period, 
year, and, month of calving, and sire upon milk yield, fat yield, and 



-•pa^gosp"!" t/v" 



4% 



FCM were studied on milk production data. First calf heifers had 
means for age, length of record, and days open, of 33 months, 298 
I ciays and 173 days, respectively. Average milk yield, fat yield, and 

4% FCM ranged between 2,910 and 3,872; 103 and 13^; and 2,693 and 
3,558 kg, respectively. Mature cows averaged 68 months, 296, 1 75 
and 98 days, for age, length of record, days open, and previous dry 
I period, respectively. Average milk yield for this group of cows 

varied from 3,685 to ^,885 kg. !n general, analyses Indicated that' 
age significantly affected yields of mature and all cows. Effects 
of age on first calf heifers were not large. Increases in yields 
to maturity varied from 12 to 30%. Lactation length significantly 
affected production In all three groups of cows studied. Days open 
did not affect significantly milk production. No significant effect 
of previous dry period on production performance of Herds 2 and 3 was 
detected. However, linear and quadratic effects were statistically 
signl f leant in Herd 1 . 

Wide variations within and between herds were observed for 
herltabillty and repeatability estimates. Pooled herl tab! 1 i ties were 
0.65, 0.31 and 0.52, respectively, for milk, fat, and 4% FCM yields. 
For the same variables, pooled repeatabi 1 i ties were O.3I, O.O8 and O.I3, 
respectively. The limitation In number of records, non-removable 
environmental correlations, assortative mating, and unusual differences 
^ in genotypes of sires represented was considered as possible factors 

contributing to the wide variation and high herltabillty estimates 
observed. The small volume of data and year to year variation In 
climatic and management could be reasons to partially explain the 
variable results found for repeatabi 1 i ti es . 



XI 



T?v:<trfTwiiaiftf:i^fc*iM 



Some ^56 records from 203 daughters of 20 different U.S.A., 
Holland, and Colombian sires were considered in a study of herd by 
sire interactions. Herd by sire components of variance surpassed 
in most cases the magnitude of the sire variances. Herd, sire, and 
herd by sire significantly affected milk, fat, and kZ FCM yields 
with exception of sires on fat yield where no significant effect was 
detected. The widely divergent origin of sires and the large envi- 
ronmental differences between herd locations partially explained 
these results. 



XI I 



m i iB —i iTri i. 



NTRODUCTION 



J 



The increasingly rapid rate of growth of the human population 
has brought a food deficit which is particularly acute in tropical 
countries. Tvjo-thirds of the world's people live in countries with 
nutritionally inadequate diets. In order to maintain their own 
population and Its anticipated growth, developing countries need to 
increase available food supplies three to S% per year. 

The future role of livestock as a source of food for the growing 
population will be dependent on more efficient animal production in 
the sub-tropical and tropica] regions of the world. Milk from dairy 
cattle is one of the possible sources of human food. It provides 
high quality proteins to a world in which a protein deficiency already 
exists, and in which the deficiency is expected to become more acute. 

From recent statistics, the world's annual milk consumption is 
69.8 kg per capita, whereas the consumption in North America is approx- 
imately three times this amount (3), Average milk intake in Latin 
American countries is estimated to be around 82.7 kg, while in Colombia 
it is only 52.6 kg. This amount is about or,e fourth of the consumption 
in North America, and is lower than that of the world average. Nutri- 
tional problems of people of tropical areas can be alleviated, in part, 
by increasing milk production in tliese areas and consequently increas- 
ing the availability of protein per capita. 

Dairy cattle performance in temperate countries has proven to be 
affected not only by genetic potential, but also by environmental 



1 



•ivrwrmiggwi 



effects such as age of cow, season, year, and msnageria] practices. 
Little information is available, however, on genetic and environ- 
mental factors affecting the productive and reproductive capacities 
of dairy cattle maintained in tropica] countries. The same lack of 
Information is found in the dairy cattle. exposed to the hot and 
humid regions, medium climate, and high altitudes of Colombia. 

Success in selection for economically important traits such as 
milk yield or reproductive efficiency in dairy cattle depends upon 
the knowledge of phenotypic, genetic and environmental parameters. 
It is believed that progress in dairy cattle in Colombia, as in any 
area of the world, will be based on well-planned research. The 
objective of the present study was to investigate the influence of 
certain environmental and geneti'c factors on milk yield and repro- 
ductive performance of three experimental Kolstein herds which have 
been maintained for a period of 12 years in three different regions 
of Colombia. 

It Is hoped that this small contribution will provide useful 
Information which might be applied to increase productivity of dairy 
cattle in the different climatic conditions of Colombia and other 
developing countries of the world. 



nTTTTTiJinmirftWinilli rnfr-in~i ■iwimn 



REVIEW OF LITERATURE 

t 
J Most of the research published concerned with factors to be dis- 

cussed in this review has been carried out in the more productive 
regions of temperate zones. Unfortunately, comparable information 
still has not been generated in tropical and subtropical regions, 
high mountain areas, or semi-arid parts of the world. 

Reproduction 



Reproductive efficiency often varies vjithin and between herds 
without any apparent reason. Losses in breeding efficiency of dairy 
cows usually can be attributed either to failure of covjs to be bred 
or to their return to heat after breeding. Variation in reproductive 
performance, in general, can be due to abnormal physiological function 
of the cow; however, the environmient to which the cow is submitted or 
the way she is handled also are important factors to be considered. 

Ca lvin g in terval 

Factors that affect the length of the period from one parturition 
to the next have been studied by several authors. In m.ost cases an 
optimum length Is considered to be approximately between 12 and 1^ 
m.onths. Maintenance of regular calving intervals of desirable length 
constitutes satisfactory breeding efficiency in cattle. 

Calving interval as one of the measures of reproductive effi- 



ciency ciin be divided into two parts: (a) the service period which 
is the period between parturition and conception, and (b) the gesta- 
tion period which is the time from successful service to parturition. 

The length of the calving interval in dairy cattle in temperate 
countries has been reported by several investigators. For example, 
Dunbar and Henderson (70) studied records of 1,015 Holstein cows in 
a program of artificial insemination (Al) in New York State, and 
found an average calving interval of 403 days. Similar results v/ere 
reported by Legates (116) vjho based his study on 2,^19 intervals from 
12 North Carolina herds. The mean interval v;as kOS days. Recently, 
Norman and Thoele (1^2) reported an average of 385 t ^5 days from 
30,000 Pennsylvania DMIA records. 

Causes of prolonged calving interval vjere investigated by Buch 
et al . ('4^). The study was based on 395 parturitions in an outbred 
experimental Holstein herd in V/isconsin. Losses of time were attr-ib- 
uted to one or more of the following conditions: (a) delayed post- 
partum anestrus, (b) interruption of the estrual cycle, (c) out-of- 
breeding condition, (d) infertile service, and (e) loss of pregnancy. 
Averaged over the entire herd, these losses amounted to 0.3, 8.0, 5.2, 
21.2, and 11.9 days, respectively.. 

An analysis of the effect of month of calving oii length of sub- 
sequent calving interval was conducted by Poston et al. (152). They 
used 2,51't records from six Holstein herds of the North Carolina 
institutional Breeding Program. The average calving interval ranged 
from 397 to 422 days for calvings in October to May, respectively. 
Differences were s i gn i P i cant (P <0.0l) for months within year and 
herd, and for herds, but not for years v^ithin herd. Andersen (12) 



mwK fc W.fuTa M Mt ' CfTO O CBi hMSJ^s^ 



studied the length of 1,782 calving intervals of Red Danish cows, 
and 2,292 intervals of Black Pied Danish cows. Calving intervals 
averaged 39^.0 and 38O.5 days, respectively. Significant differences 
due to season of calving were observed. in both breeds cows calving 
in April had the shortest calving interval. 

It has been shown that calving interval as a measure of repro- 
ductive efficiency has a very low her i tabi 1 i ty. Dunbar and Henderson 
(70) indicated that selection for fertility, measured by calving 
interval, cannot be very effective. The heritability of this trait 
in their study v^as estimated to be zero. Legates (II6) also found 
the heritability of calving Interval to be zero in a study of 1,016 
dairy cows from North Carolina. Norman and Thoele (1^2) found that 
intra-herd her I tabi 1 i ties ranged from 0.02 to 0,04, and Andersen 
(12) observed values of 0,012 and 0,056, respectively, for Red 
Danish and Black Pied Danish cows. On the other hand, higher 
estimates of heritability for breeding efficiency have been found. 
Wilcox et al. (206) mieasured the reproductive performance in a 
Holstein herd by using formul asbased on calving interval. Herita- 
bility of breeding efficiency observed in this study was 0.32, In 
beef cattle, Deese (6^) studied records from a purebred Brahman herd 
and a crossbred foundation herd in Florida. Heritability estimates 
for calving rate calculated by different methods ranged from 0.21 
to 0.63. 

The reproductive behavior of European dairy breeds subjected 
to tropical environment has been in many cases disappointing. The 
lower reproductive performance of these breeds in the tropics, as 
compared with the same breeds in temperate zones, could be attributed 



■ ta . -s ^ -L e -fc w — rcm i h— fcjik K 



6 

to the combined effect of poor management practices, and the climatic 
effects upon the different physiological processes. 

Carneiro and Lush (52) studied Brown Swiss cattle in Brazil, 
and reported a calving interval of kSk days based on approximately 
1,000 calvings. Carneiro at al, (5I) found intervals of 531 t 17. Q, 
^8 .. 6.0, if38 1 15.0, and '+20 t 12,0 days for Holstein, Brown Swiss, 
Guernsey, and Jersey cows, respectively, in Brazil. Rios and Bodisco 
(159) reported an interval of ^65 t 38.2 days for Brown Swiss cows 
under experimental conditions at Mai'acay, Venezuela. Carmona and 
Munoz (50) analyzed 2^1-6 calvings of Jersey and crossbred Brown Swiss- 
Zebu cows in Turrialba, Costa Rica, Results showed calving intervals 
of 384 and 413. days, respectively. El-Sheikh and El-Fouly (74). 
studied 832 intervals of Friesian cows in U.A.R. The average lengths 
of the first four calving intervals were 4/4, 399, 392 and 344 days, 
respect ivel y . 

Reproductive performance based on calving intervals of some 
native breeds in tropical areas has been reported. In most cases 
calving intervals were shorter than those reported for European 
breeds under tropical conditions. Mahadevan (123) studied Sinhala 
cattle in Ceylon and found an average calving interval of 355 days, 
De Alba and Carrera (62) indicated an interval of 386,7 days for 
milking Criollo cows under conditions of Turrialba, Costa Rica. 
Similar results with the same breed were also found by Carmona and 
Munoz (50), Bodisco et al. (35) studied the performance of milking 
Criollo covjs under range conditions of Rio Limon, Venezuela.. They 
observed a calving interval of 372 t 3.5 days, Bodisco and i'lazzari 
(34) reported 415 t 3.0 days for the same type of cows at Maracay, 



Venezuela. Alim (6) studied 393 gestations of Kenana cattle in 
Sudan and found an average interval between births of 395 t 4.30 
days. Pearson at al, {]kS) reported calving periods of 372 and 392 
days, respectively, for the native breed BON, and contemporary ]/h 
Jersey ■• 3 A BON crossbreds in Colombia. 

Calving interval in Kenana cattle of Sudan varied significantly 
due to age of cow, Alim (6) observed that calving intervals were 
longer for younger cows than for older animals. Sharda et al. (172) 
also found that calving interval was longer following the first 
calving and shorter after the second calving of Hariana cows. Cows 
which calved during the period from March to June tended to have 
longer calving intervals than those calving during other months. 

Amble et al. (8) studied 7,700 records from six Indian dairy 
breeds. Her i tabi 1 i t i es for calving interval were found to be 0.20, 
0.38, 0.34, 0.11, 0.91 and -0.54; and repeatabi 1 i ties 0.47, 0.40, 
0.50, 0,37, 0.54 and 0.50, respectively , for Red Sindhi (two herds), 
Kangayam, Tharparkar, Gir, and Kankrej cattle, A negative dam- 
daughter correlation was found by Singh and Prasad (I76) for intervals 
of Hariana cattle in India. The repeatability calculated by intra- 
class correlation was 0.2^46 t 0.053. Kushwaha (II3) found heri ta- 
bi 11 ty and repeatability for Sahiwal dairy cows to be Ojg and 0,34, 
respectively. For the same type of cows, Johar and Taylor (101) 
reported heritability of 0,28 t O.O6 from the intra-sire regression 
of daughter on dam, and repeatability of 0.4l6. 

Ca 1 y i nq Da.t£ to_FJxsJ:_ Heat 

The length of service period is determined by the managem.ent 
policies of the herd and reproductive status of the cow and sire 



8 

as well as hereditary tendencies. However, in studying length of 
service period it is necessary to consider intervals such as calving 
date to first heat, first heat to first service, and first service 
to conception or successful service. 

It is apparent that one of the factors that affect reproductive 
efficiency in dairy cattle is the length of time from calving to 
first heat. Maintenance of regular calving intervals of desirable 
length depends in part upon the reproductive status of the cow when 
rebred after a suitable interval postpartum. Studies on this phase 
of the reproductive cycle in dairy cattle have demonstrated that 
the fertility of cows is low immediately after calving, and for 
this reason it is recommended that cows not be serviced until at 
least 60 days after calving. In a study of 291 range cattle, Lasley 
and Bogart (11^) found that of 35 cows bred from 10 to 40 days after 
calving, A-8.6% settled with one insemination, whereas a maximum 
fertility of 75% conception with -one insemination v;as obtained in 
12 cows bred from 161 to I90 days after calving. Erb and Shaw (75) 
reported in a summary of breeding failures in Washington that there 
was an apparent improvement in breeding efficiency by waiting at 
least 50 days after calving before breeding. 

Chapman and Casida (5'i-) found that the average interval from 
calving to first heat in dairy cows was 59 t 39 days. in abnormal 
cows, where cystic follicles or retained corpora lutea had been noted 
previously, the period was 71 days. 

Clapp (56) studied records of I59 pure Holstein cows from 
Wisconsin and found the interval from calving to first estrus to be 
69.^ days for cows milked four tim.es per day, 7I.8 days for nurse 



9 

cows, and k6.h days for cows milked two times daily. He stated that 

the frequency of suckling or handling of the teats in milking was 
the main cause of the difference in length of the interval. 

Herman and Edmondson (89) calculated the days from calving to 
occurrence of the first estrus in 3k7 dairy cows which had completed 
968 normal parturitions. They found an average interval of 57 ^ 28 
days. Age of the cow was a factor influencing this interval. In 
fact, it was longest, about 75 days, for first-calf heifers (1--1/2 
to 2-1/2 years), shortest, or about 50 to 60 days, for cows from 
2-1/2 to 7 years, and increased again to between 60 and 90 days for 
cows more than seven years of age. 

Buch at al. {kk) reported an average interval of 33 days from 
322 normal calvings of Holstein cows in Wisconsin. They found that 
cows calving during summer tended to come in heat earlier (28 days) 
than those calving in the other seasons (3^ days), whereas those 
calving during winter had the longest intervals (38 days) from 
parturition to first heat. Buch et a], (if3) found that the interval 
from parturition to involution of the uterus was kj days and that 
this interval was influenced significantly by age of the cow, being 
k'Z days in primiparous and 50 days in pluriparous. Also, significant 
differences were observed among seasons, being shortest in the 
summer and fall. Casida and Venzke (53) found that approximately 
26 days vjere required following calving for the uterus to return to 
normal position, tonus and size. Similar results were reported by 
Morrow et al. (137) wIto found that uterine involution was almost 
complete by 25 days after normal calving. They observed average 
intervals from calving to first heat of I5.O days after normal calvings 
and 3'^i--'+ days after abnormal calvinas. 



Hirt (94) studied 2,760 records from German Spotted Mountain 
cattle, and indicated that the period between calving and first 
heat to be 83-5 days. He also found that this period was not in- 
fluenced by heredity, lieritability values near zero viere reported 
by Carman {kS) who studied two experimental Holstein herds in Iowa. 
He found mean length of calving intervals to first heat of 55, it and 
71.0 days, with repeatability estimated to be 0,15 and 0,27, respec- 
tively. On the other hand, heri tabi 1 i ties of 0,27 and 0,32 were 
reported by Olds and Seath (1^5), They based these estimates on 
the intrasire regression of daughter on dam using the first available 
record and all records, respectively, for each animal. They concluded 
that the relatively fixed physiological characteristics determining 
the interval from calving to first heat in individuals seemed to be 
for the most part inherited. This study was based on ^72 normal 
lactations from the Kentucky Experiment Station dairy herd. 

The average interval between calving and the first postpartum 
heat in Friesian cows under Egyptian conditions was studied by 
Dessouky and Rakka (66), and was found to be 85,52 t 2.15 days. 
Season of calving had a significant effect. Intervals of 90. ^^i, 
71.5^, 95.0, and 126. '47 were observed for cows calving in winter, 
spring, summer, and fall, respectively. Mies Filho and Costa 
Aroeira (136) reported a mean interval of 87 days obtained from 75 
Gir dairy cows in Brazil, Fallon (79) investigated 383 Jersey cows 
in South Eastern Queensland, and found that the mean interval between 
parturition and first heat was ^0.45 t 22.70 days. He indicated that 
fertility at first heat was a function of the postpartum interval 
rather than of any characteristic of first heat per se. 



11 

Information concerning the interval between first heat and 
first service is very scarce. However, this interval would basically 
influence the length of the service period. Chapman and Casida (54) 
reported that the average length of service period in eight Holsteln 
herds in Wisconsin varied from 120 to I80 days. In one of the herds, 
the service period was I50 days, of which 50 days was the period from 
first heat to first service. 

Fir st Se rvice to Con ception 

Chapman and Casida {5k) studied the length of interval from 
first service to conception in the records of five Holstein herds 
from Wisconsin and found an interval of 30 days. Tabler et al. (I86) 
analyzed 19 cow families of the Ayrshire breed and observed an 
average of ^9 days. He also reported a greater variation within 
families than between families, and significant differences due to 
sire effects, Pou et al, (1 53} found a mean interval of 52 days 
for a similar period in the Beltsville dairy herd. Carman (48), 
from data of two Holstein herds in Iowa, reported means of 28 t I.7 
and 42.0 „ 2,7 days, respectively, and found that years, season, and 
age of the cow had little effect on the number of days to conception. 
Cooper et al. (58) analyzed 6, 1-94- cal vi ngs from Kentucky DH!A herds, 
and indicated that variation in number of days from first service to 
conception accounted for 61% of the variation in calving interval. 
Repeatability and heritabllity values for breeding efficiency 
based on tlie number of days from first service to conception were 
estimated by Pou et al, (153). They used the values of the coeffi- 
cients of cow variance and error variance to estimate repeatabi 1 i t ies 



12 

and daughter-dam cross-products for heri tabi I i ties. Values obtained 
vjere 0.!] and 0,07, respectively. Smaller repeatability and her! ta- 
bi lity values were reported by Carman (48). Based on the estimates 
of components of variance, and utilizing data from the New York 
Artificial Breeders, Dunbar and Henderson (70) reported repeatability 
of non returns to first service to be 0.027. Heri tabi lity of non 
returns to first service was found to be 0.00^!+. 

Services per Co n ce p t i oji 

Conception rate, as calculated by the number of services required 
for each pregnancy, has been one of the most popular criterion used 
as a measure of breeding efficiency. 

Some of the factors that affect the number of services per con- 
ception in herds free of disease are fertility of the bull, fertility 
of the cow, age of the cow, cl imatol ogi cal conditions, nutritional 
level, and management in general. 

Extensive informiation on conception rate has been published in 
temperate countries. Boyd at al. (39) analyzed 29 herds serviced 
by the Kentucky Artificial Breeding Association, and found that the 
mean num.ber of services per conception was 1.68 - 0.7^. Carman (48) 
investigated the breeding efficiency of two experim.ental Holstein 
herds in Iowa, and found means of 1.8 1' O.36 and 1.7 t 0.33, respec- 
tively, Tanabe and Salisbury (I87) studied 12,621 complete recorded 
services of registered Holstein cows under the A.!, program in New 
York, and found average services per conception of 2.07 with a breed- 
ing efficiency of 48,2%. VanDemark and Salisbury (194) studied 
1,674 pregnancies of cows from the University of Illinois dairy herd, 
nd indicated that 1,97 services per conception were required. 



a 



13 

Legates (116) studied 1,129 records from 12 North Carolina herds, 
and found that the mean service per conception was 1.80, 

The heritability of services per conception v^-as estimated by 
Legates (116) to be 0.026. Ma concluded that the number of services 
required per conception for one calving is of no value in predicting 
the number of services that will be required for a subsequent preg- 
nancy. Carman (48) reported values of heritability and repeatability 
close to zero. Also, very little genetic variability in services per 
conception was found by other investigators such as Trimberger and 
Davis (191), Olds et al, {\kh) , and Tabler et al. (186). 

However, Berge (29) studied data of the Norwegian Agricultural 
College herd, and found that the repeatability of conception rates 
at different calvings of the same cow was 0.22 t 0.05. 

Singh (1/3) studied data on 687 calvings of Tharparkar cows, 
and found that the number of services per conception was 1,76 t 0.0^6. 
The heritability calculated from paternal half-sib correlations was 
"0,048 for the first pregnancy and 0,147 for the first three preg- 
nancies. 

The number of services per conception of European cattle in 
tropical areas is in most cases higher than those observed in tem- 
perate countries, Joubert (105) conducted investigations in South 
Africa, including Holstein heifers r-'^'ised on a hich and low plane of 
nutrition, and found services per conception of 3,33 and 2,33, 
respectively. Carmo and Batista (49) reported 3,84 t O.63 services 
per conception for l!olstein cows under experimental conditions in 
Brazil, Rubio and Salazar (166) observed services per conception 
of 4,6 and 6,4, respect! vely, for Holstein and Brown Swiss cows in an 
experimental station in Colombia. 



Gestation Length 

The period between successful service and parturition is ttie 
second part into which calving interval is divided. In order to 
study the different factors associated with this period in dairy 
cattle, several investigations have been carried out in temperate 
as well as in tropical countries. 

Mean gestation lengths of different breeds of dairy cattle were 
summarized by Andersen and Plum (13). Means varied from 279,4 days 
for Holsteins to 290.9 days for Brown Swiss. The mean gestation 
length of Holstein cattle from temperate countries has been observed 
to vary from 275.6 days, as reported by Foote et al, (82), to 281,9 ± 
0.19 <^ays as reported by During (71). 

Gestation periods of h'ol stein cows in tropical areas viere 
studied by Veiga et aK (198) who found 276 !' 0,39 days for Holstein- 
Friessan cows In Brazil, Similar results were observed by Grossman 
and De Oliveira (87) in their study of Holstein cattle also in Brazil. 
Dessouky and Rakka (66) studied the gestation period of Friesian 
cattle In Egypt and found an average of 282.3 t 10,30 days. Ward 
and Castle (202), based on 2,228 gestations of dairy cattle in New 
Zealand, found an average length of 282.6 t 5.1 days. 

Studies of various native breeds from tropical areas have been 
reported and in general It has been observed that the duration of 
their gestation periods was longer than those observed in cattle 
from temperate countries, Jordao and Veiga {]0k) studied 98O gesta- 
tions of Caracu cows in Brazil and found an average gestation period 
of 286,9 t 0.35 days. Joubert and Bonsma (IO6) reported 295.0 t 0.32 
days for Africander cows, Ragab and Asker (155) reported 289.5 t 7.2 



days for Egyptian cows, and Kolhi and Suri (111) observed average 

-j- 

gestation period of 290,7 - 0.90 in Marian cattle from India. 

The effect of season on gestation length has been studied by 
several authors. Herman et al. (91) analyzed records from the 
Missouri Station herd and found that cows calving during fall and 
winter months carried their calves an average of one to three days 
longer than those cows which calved during the spring and summer 
months. Also, shorter gestation periods for cows calving during 
the summer were observed by Alexander (5) from a study with dairy 
breeds in Mlinois. Joubert (105) indicated that pregnancies of 
South Devon cows ending during the winter tended to be longer (288.4 
days) than those ending during summer (285.8 days). 

Ragab and Asker (IS'-O reported a significant effect of month of 
calving on length of gestation in Egyptian cattle. Chaudhuri and 
Sinha (55) found shorter gestation periods in Tharparkar cows when 
climatic conditions were milder, and longer when calving occurred 
in the wet season. Month of calving also had a significant effect 
on gestation length in the study carried out by Kohli and Suri (111) 
with Mariana cattle in India. 

HovjQver, several investigators have reported that season of the 
year had no effect on gestation iength. Gestation length vjas not 
affected by seasonal differences according to Rollins et al, (162) 
in their stLidy of inbred Jersey cows in the University of California 
herd, Lazarus and Anantaki shnan (115) did not find any significant 
influence of month of calving on gestation length of Indian cattle. 
Similar results were reported by Dessouky and Rakka (66) for Friesian 
covv'S under Egyptian conditions. 



16 

The effect of sire on gestation period has been studied by var- 
ious authors. Some have indicated that service sire had an influence 
on gestation length," Analysis of 2,824 gestation periods of Holstein 
cows from V/ashington was made by Knott (IO9). He observed that 
gestation periods of caives sired by some bulls were definitely longer 
or shorter than average, and indicated the possibility of paternal 
influence. Also, Alexander (5) indicated that sire affected length 
of gestation, based on his study in Illinois with the five major 
dairy breeds. Brakel et al. {hO) compared mean gestation lengths 
resulting from the use of different sires and found significant inter- 
sire differences in Holstein, Jersey and Ayrshire breeds. Significant 
differences between sire line's were also observed by Foote et al. 
(82) in their study of 258 Holstein cows from V/i scons i n. 

Ragab and Asker (15^) studied 855 calvings of Egyptian cows and 
163 calvings of Dairy Shorthorn cows and found that sire of the calf 
had a significant effect on gestation period. Similar results were 
also reported by Ahmed and Tantawy (k) in a later study carried out 
with 180 Egyptian cows. Significant differences were also reported 
by Kohli and Suri (111) in their study of 797 gestations of Hariana 
cattle in India. Joubert and Bonsma (IO6) found that the sire may 
have a significant effect on the cow's gestation period, Tiieir study 
was based on 827 gestations of pure and crossbred Africander cows. 
On the other hand. Briquet and De Abreu (42) reported that length of 
gestation appeared not to be influenced significantly by sire. Their 
study was based on records of 2i0 Zebu cows from Brazil. 

Several researchers have indicated that age of dam affected the 
length of the gestation period and that adult cows carry calves for 



) 



17 

a longer period than younger cows, Knott (IO9), from data obtained 
on 2,910 gestation periods of Hoi stein cov\/s , observed an increase 
of approximately one to one-half days as the age of the dams in- 
creased froui: 2 to 6 years. Brakel et al , (40) studied records from 
the Ohio State University purebred dairy herd. They observed that 
cows 5 years old and over exceeded those of 2-years old by 1.5 days 
in length of gestation. The difference obtained v;as highly signifi- 
cant. Herman et al, (sO studied records from the Missouri Station 
dairy herd. Their results indicated a slight increase in gestation 
length for mature covis , compared to the gestation period of first 
and second calf heifers. Stallcup et al. (181) investigated gesta- 
tion records of the Arkansas Agriculture Experiment Station dairy 
herd and found that mean gestations of cows 5-years old and o\/Qr 
exceeded those of 2-year old cows by 1.6 and 1.5 days in Hoi stein 
and Jersey breeds, respectively. Sizable regression coefficients 
for first calf heifers were found by Wilcox and Staffa (208) in 
study with dairy cattle at Florida Experimental Station, They 
suggested that age of dam might influence birth weights and gestation 
lengths. 

On the other hand, there are other Investigators who have re- 
ported that gestation length was not influenced by age of the dam. 
Copeland (59) studied 1,075 gestations of Jersey cows in New York, 
He observed that age of dam apparently had no effect on length of 
gestation. The same conclusion was indicated by Davis et al, (60) 
who based their study on 755 normal gestations of Hoi stein covjs in 
the University of Nebraska herd, Wilcox and Roy (207) from analyses 
of 1,30^ normal parturitions of Jersey cows (first calf heifers omitted) 
indicated that gestation lengths were not influenced by age of dam. 






18 

Briquet and De Abreu {hi) studied data taken from indian breeds 
at Minas Gerais, Brazil. They concluded that length of gestation 
appeared not to be influenced significantly by age of cov-j. However, 
data on age were rather limited, Singh et al . (177) did not find 
significant effects of age of dam on gestation length of Tharparkar 
cows in India. Al so, . Joubert and Bonsma (1C6) reported no effect 
of age of dam on length of pregnancy of pure and cross-bred Africander 
cows . 

Some authors have shown that gestation length was influenced 
by weight of dam. Foote et al. (82) reported a positive correlation 
between weight of dam and gestation length in 536 gestations of 
Wisconsin Holstein cows. Similar results were reported by 
Anantakri shnan et al. (11) and Kohli and Suri (111) In their study 
with Indian cattle, and by Ahmed and Tantawy (^4) with Egyptian cows. 
However, Vukavic (200) working with SImmental and Makela and Oittila 
(129) with Ayrshire cattle did not find any correlation between 
weight of dam and gestation length. 

Several investigators have reported that average gestation 
length for cows carrying male calves was longer than for those carry- 
ing female calves. Herman and Spalding (90) studied 962 Holstein 
records from the Missouri Station herd, ana found that the average 
gestation length for cows carrying males was 278,75 ~ 5-9^ days and 
for those carrying females was 277. 5I t 3.79 days. Brakel et al. 
{kO) in their study of records of the dairy herd of Ohio State Uni- 
versity found that sex of calf affected gestation length significantly. 
Gestation preceding the birth of 631 male calves averaged 0.77 days 
longer than 625 gestations preceding the birth of female calves. 



a i^ ar^ ii Fvi fi y?i i »WJ W w I j | g' J rT:r"rr'jon^ =tfswwfyqg'=' 



19 

Significant differences were also observed by Braude and Walker (k]) 

in their study of Dairy Shorthorn cows in England. They found that 
bull calves were carried longer than heifer calves by an average of 
1.68 days. Rollins et al. (162) analyzed records of 1 ,353 gestation 
periods of inbred Jersey cows from the University of California herd. 
They found that male calves were carried in utero 2 days longer than 
female calves. This difference was highly significant. The effect 
of sex of calf was also found statistically significant by DeFries 
et al. (65) with data representing the five major dairy breeds from 
the University of Illinois herd. in general, male calves were carried 
about K5 days longer than females. 

On the other hand, some studies have indicated that sex of calf 
has no influence on gestation length. Davis et al. (60) studied 
755 gestations of Holstein cows from the University of Nebraska herd. 
They found that length of gestation was not influenced by the sex of 
the calf. The average gestation length for males was 278.9 days and 
for females 2/8.^ days. Also, Dessouky and Rakka (66) observed that 
gestation length of Friesian cattle in Egypt was statistically un- 
affected by sex of calf. Average gestation lengths of 283.83 t 13.22 
and 281.85 _ 24,38 days were found for male and female calvings, 
respectively. Singh et al. (I/7) with Tharparkar cows in India 
reported also nonsignificant effects of sex; however, the average 
gestation period was 289 1" O.^i^ days for males and 287 t 0,48 days for 
females. The average gestation period of male and female purebred 
Friesian calves observed by Jum.a and Kassir (IO7) in India was 275,7 
and 274.8 days, respectively. However, 278.4 and 274.9 days for male 
and female crossbred Friesian (mainly 7/8 and I5/I6 Friesian) were 
observed in the sam.e study. 



"nifcriia.wii.li rijiia^r^fcii tcfr^ — s^ 



20 

. Estimates of heritabiiity for gestation length in cattle have 
been found in a number of studies. These estimates are quite 
variable; hovyever, the majority of them fall from O.3O to O.50. 

The average length of 38^+ gestation periods of Holstein cows 
from Wisconstn was studied by Jafar et al, (96). They reported a 
hers Lability estimate of O.kQ. Rollins et al. (162) analyzed the 
records of 1,353 gestation periods of the University of California 
-Jersey herd and observed a heritabiiity of 0,30, They concluded that 
sire influenced the length of time his offspring were carried in the 
uterus. Brake] et al. (kO) also studying the Jersey breed found a 
heritabiiity estimate of 0.^0. Similar results were observed by 
DeFrles et al, (65) who estimated the pooled heritabiiity based on 
paternal half-sib correlation to be 0.'l7 by analyzing 2,063 gesta- 
tions representing the five major dairy breeds from the University 
of niinols herd. Rendel (I56) studied 3,500 gestation periods of 
Swedish breeds of cattle and, based on the paternal half-sib correla- 
tion, found a heritabiiity of 0.064. Everett and Magee (78) from 
7^7 pregnancies of Holstein cows in Michigan reported a heritabiiity 
of 0.10. They also indicated that year and season did not affect 
significantly duration of pregnancy. Higher heritabiiity values of 
0,60 t 0.12 were reported by Plum et al. (150) in their study of 958 
Holstein calves, after the data had been adjusted for effects of herd, 
sex, parity, year, and season. 

Singh et al. (I77) estimated the heritabiiity of gestation peri- 
od in a herd of Tharparkar cows in India, and based on the paternal 
ha|f~sib correlation, found a value of 0,320 t O.83, Heritabiiity 
estimate of O.5O was reported by Wheat and Riggs (204) in beef cattle. 
In general, the reported results on the factors affecting gesta- 



) 



21 
tion length are quite variable. Hov/ever, Mahadevan (126) stated that 
even though these results are rather conflicting the absolute varia- 
tion in gestation length is not large, and, if such variations occur, 
may be regarded as having little practical significance. He finally 
concluded, in view of the relative constancy of the gestation period, 
that the principal factor controlling variations in the caiving 
interval is the service period, 

Bi rth Weight 

Birth weights of dairy calves have been studied by several 
authors from temperate countries as well as from tropical ones. 
Average birth weights (mean for both sexes) for the five main dairy 
breeds vary from kS.o t 1.8 lb for the Jersey breed as reported by 
Donald et al, (69) to 102,6 t 3.0 lb for the Brown Swiss breed as 
reported by Legault and Touchberry (118). Andersen and Plum (13) 
reported average birth weights for the Holstein breed varying from 
88 to 96 lb. 

Calves born from mature cows are generally heavier than those 
born from first calf heifers. Most of the authors are in agree- 
ment that age of the cow affects birth weight of the calf. Tyler 
et al. (192) analyzed 75^- records from three Holstein herds of 
Wisconsin and concluded that first calf heifers in general gave 
birth to lighter weight calves of both sexes than older cows. 
Similar results were reported by Davis et al, (60) in their study 
of 755 gestations of Holstein cows from the University of Nebraska 
herd. They found that the calving sequence of the dam had a signif- 
icant influence upon birth weight of the calf. Stone et al, (182) 
found a highly significant correlation between birth weights of female 



22 

calves and age of the dam, for both Holstein and Jersey breeds under 
Louisiana conditions. Foote et al. (82), in their study of 536 
gestation of Holstein cows from Wisconsin, found also that birth 
weight increased significantly with the parity order of the dam. 
Legault and Touchberry (118) studied 1,23^ birth v^eights represent- 
ing the five major breeds of dairy cattle from the University of 
Illinois herd. They found that first calves were significantly 
lighter than all subsequent calves. McCandlish (13^0 studied 369 
calves of the four main dairy breeds from the i owa State dairy farm. 
He found that as cows increased in age up to 5 years, the average birth 
weight of the calves increased, and from then on there was an irregular 
decrease in the vyelghts of the calves, Braude and Walker [k]) studied 
records of 230 dairy Shorthorn calves in England and found that calves 
from the third or subsequent lactations are heavier than those from 
the first or second lactations. 

Asker and Ragab (20) in a study carried out with Egyptian cattle 
found that sequence of calving was responsible for bringing about 
significant differences between birth weights of calves. Some influence 
of the calving sequence on the birth v/eight of the calves was also 
observed by Anantakr i shnan and Lazarus (10) in Indian cattle. Varia- 
tions due to calving sequence were also reported by Roy and Goswami 
(165) in Zebu x Friesian cows. Age of the dam at calving v^as also 
significantly correlated with birth weight of purebreds (0.55) and 
crossbred (0.29) Friesian calves as was found by Juma and Kassir (107). 

On the other hand, some investigators have reported no relation- 
ship between birth vjeight of the calf and age of dam. Bachner (21) 
did not find any correlation between these tv;o variables in his study 



23 

of Spotted Mountain cattle. Similar Findings viera reported by Jordao 
and De Paula Assis (103) of data taken from Meuse-Rhi ne-Yssel cattle 
at Sao Paulo, Brazil, Birth vjeights of 771 Mariana calves in India 
were studied by Kohli and Suri (ill). They did not find any signif- 
icant effect of calving sequence number on birth weight, Bhalla et 
al. (30) found also that birth weight of Sahiwa] calves vjas not 
significantly correlated with age of the dam. 

That the weight of the dam has a positive correlation with the 
birth weight of the calves has been confirmed by several researchers. 
Correlations of 0.13 and O.'il have been reported by Makela and Oittila 
(129), and Anantakrishnan et al. (11), respectively, in their studies 
with Ayrshire cattle. 

Some investigators were in agreem.ent that season of year had 
little or no effect on birth weight of calves, Tyler et al. (192) 
studied birth weights of offspring of six Holstein sires in two 
Wisconsin herds. They did not find any significant differences be- 
tween years or seasons. Similar results were reported by Martin (132) 
who studied 659 dairy calves from the Iowa State College dairy herd. 
Birth weights of Jersey calves were essentially unaffected by month 
of birth in the study reported by Viilcox and Roy (207). 

Asker and Ragab (20) indicated LhaL month of calviiig appeared to 
have no effect on birth weight of Egyptian cattle. Month of calving 
likewise had no detectable influence on birth weight of Red Sindhi, 
Gir, or crossbred Gir x Ayrshire calves, as reported by Anantakrishnan 
and Lazarus (10). 

However, Bhalla et al, (30) reported that birth weight of Sahlv-val 
calves was significantly affected by season. Month and season of 



2k 

calving had also highly significant effects on birth weight of pure- 
bred Friesian calves studied by Juma and Kassir (107). Vii nter-born 
calves ayeraged 3^.1 kg whereas 32.3, 28,3, and 33', 3 kg were observed 
for calves born In spring, summer and fall, respectively. 

There is a general agreement that male calves are heavier at 
birth than female calves. Sex differences in birth weight of calves 
seem to be important within the Holstein breed. Various authors have 
indicated a range in birth weights from 92.9 to 101.0 lb for males and 
from 85.5 to 94.0 lb for females. !n an early study, Eckles (72) 
reported upon ^33 calf weights obtained from the dairy herd at the 
University of Missouri. He stated that male calves averaged from 
5 to 8% heavier than females. McCandlish (134) summarized 369 calf 
weights from the 1 ovja State College dairy herd. Male calves averaged 
72 lb which was 10% heavier than females which averaged 69 lb, 
Holsteins were largest, followed by Ayrshires, Guernseys, and Jerseys, 
Fitch et al, (Bl) summarized data concerning Holstein, Ayrshire, 
Guernsey and Jersey calves dropped in the dairy herd at Kansas State 
College and found that male calves were ^l to 1 1 lb heavier 
than female calves. The average weight of all bull calves studied 
was 7.8% heavier than females. Tyler et al, (192) studied 79if 
Holstein calves in three unrelated herds f rom Wi sconsi n. They in- 
dicated that male calves averaged 5,2 lb heavier than females. In a 
study of 755 Holstein calves born at the University of Nebraska, Davis 
et al. (60) reported that the average birth weight for males was 
96.7 lb while for females it was 90,3 lb. These differences were 
significant at the 1% level. Foote et al. (82) in their study of 
536 gestations of 258 Holstein cows found that male calves averaged 
5.92 lb heavier at birth than females. Legault and Touchberry (118) 



=ss w»T ia. * « r ^ -^ j**jaaia^aa<i8iHfciky»?t£wiamiw ^i»e ^ ^ i r ri MeiWn i^ ii ii Mw il gifi iM 



25 

analyzed data from the University of illlnois dairy herd consisting 
of 1,23^1- birth weights representing the five major dairy breeds. 
They found also that bull calves were significantly heavier than 
the heifers. 

Average birth weights of 21,21 1' 0.63 and 19,-^3 t O-'^S kg, 
respectively for male and female Sahiwal calves were reported by 
Bhalla et al. (30). Beckhit and Mathout (25) reported birth weights 
of 32,5 and 30,7 kg for male and female Friesian calves, respectively, 
of an imported herd in Egypt. 

On the other hand, birth weights of I33 pure and 82 crossbred 
Friesian calves were studied by Juma and Kassir (107) in India. 
They found that the weight of calves was not significantly affected 
by sex. Average weight for males was 32,^1 kg, while female calves 
weighed 32.23 kg. 

it has been reported by several Investigators that sire had an 
influence on the birth weight of the calf. Fitch et al, (81) from 
their study with dairy cows at Kansas State College indicated that 
sire may have the ability to influence the birth vjeight of the calves 
to a certain degree, Foote et al. (82) observed significant differences 
between six sire lines of h'olsteins. Also, Roy and Goswami (I65) found 
in India that sire had a significant effect on the birth weiaht, of 260 
crossbred Zebu x Friesian calves. However, Abelein and Ritter (2) 
reported that sire did not affect birth v«/eight. 

A positive correlation oF the birth weight and length of gestation 
has been observed by several authors in dairy cattle. Positive corre- 
lations between 0,25 and 0.52 have been obtained in these studies, 
Jafar et al. (96) studying 76 Holstein calves found a highly signifi- 



-.^.'J ■C-.;.ir-.».^^-^-..-p^^..-p^-^..^^^ ...^ 



26 

+ 



cant positive correlation of 0,52 - 0,10 when adjusted for sex. 
Brake! et al, (kO) reported a definite relationship betvjeen mean 
gestation length and biirth weight of about 300 dairy calves. Corre- 
lations of 0.2it, 0,5^, 0.15, 0,26 and 0,2.9 were observed for Holstein, 
Brov«^n Swiss, Guernsey, Ayrshire and Jersey calves, Davis et al, (60) 
studied 755 normal gestations of Holstein calves and found that the 
correlation between gestation length and birth weight was 0,26. The 
regression of birth weight on gestation length was 0.66 lb per day, 
DeFries et al, (65) studied 2,063 gestations representing the five 
major dairy breeds. The observed correlations between birth weight 
and gestation length were 0.^7, 0,3^, 0.3^, 0,37 and 0.12, respectively 
for Holstein, Brown Swiss, Guernsey, Ayrshire, and Jersey, Pxegression 
of birth weight on the length of -the gestation period indicated that 
calves carried cna day less than average are approximately 1 lb 
1 ighter than average at birth, 

Ragab and Asker (iS'i-) found that there was a positive correlation 
(0,-3l8) between gestation period and birth weight of 855 calves from 
Egyptian cows. Also, Ahraed and Tantawy {k) found highly significant 
correlations in another study with Egyptian cattle. 

However, som.e studies have shown that the correlation between 
birth weight and gestation length was v'ery small or nil, in an 
early study, Eckles (72) concluded that the length of the gestation 
period was not correlated with the size of the calf. The same con- 
clusion was also reported by McCandlish (13^1) and Fitch et al. (81). 
However, all 3 studies were based on a rather small number of animals. 

Most of the literature, reviewed concerned with heritability and 
repeatability estimates for birth weight of calves pertained to beef 



j 



27 

cattle, Heritability values of 0.11, 0.22, 0.35 v-jere reported by 
Dawson et al. (61), Burris and Blunn {kj) , and Koch and Clark (110), 
respectively. Repeatability estimates for beef calves were found to 
be 0,26 in the study of Koch and Clark (llO), and 0.18 in the study 
■ of Taylor et al. (188), 

On the other hand,onlya few investigators have studied the 
heritability and repeatability estimates of birth weight of dairy 
cattle, Tyler et al, (I92) analyzed data of Holstein calves from 
Wisconsin and found the average of estimates of heritability to be 
approximately O.6O. They stated that apparently between 50 and 70% 
of the variation in birth weight of the calves studied was heritable 
after adjustment for sex of calf and calving sequence of dam. Black- 
more et al, (31) calculated a heritability of birth weight of 0,56. 
The estimations were based on the intrasire regression of offspring 
on dam of 295 pairs of Holstein cattle from Iowa, Legault and Touch- 
berry (118) studied 1,234 birth weights representing the five major 
dairy breeds from the University of Illinois dairy herd. The pooled 
within-breed estimates of heritability of birth weight obtained from 
paternal half-sib correlation, intra-sire regression of offspring on 
dam, and full-sib correlation were O.38, 0,48, and 0.5I, respectively. 
They also stated that it should be relatively easy to change the 
average birth weight of a population by selection. Recently, Roman 
et al, (164) studied birth weights of 2,125 Jersey calves in a Florida 
herd, and found that nonmaternal heritability of birth weight was 0,52, 
maternal 0.84, and total 0,20, 

Asker and Ragab (20) workirg with Egyptian cattle obtained a 
heritability estimate for birth weight of 0.417, and repeatability 



rtetmwip^TtafcTi-F — msi 



28 

of birth weight for 133 purebred Friesian calves under Indian condi- 
tions was reported by Juma and Kassir (IO7) to be O.Q7, 

Reasons for Disposal 

It is important to know the causes for which certain cows leave 
^ the herd while others remain, because it is only through information 

of this kind that i mnrovemen t can be rnade. 

Seath (171), in a study of 37 Kansas Cow Testing Association 
herds with a total of 1,26^ cows found that cows left the herd be- 
cause of the following reasons: 39% disease, 31% low production, 19% 
dairy purposes, and for other causes, 7%. Asdell (16), in an ex- 
tensive study, reported the reasons for culling 2,792,188 DHIA cows 
on test in I7 different states. The percentages were 33.5, 23.4, 
11.5, 8.2, 7.4 and 5.0 for low production, dairy purposes, udder 
trouble, sterility, abortion and death, respectively. Based on 7,362 
cows from New York herds, O'Bleness and Van Vleck (1^3) reported the 
most important reasons for disposal to be low production, 27-32%; 
sterility, 16-19%; udder trouble or mastitis, 14-20% and sold for 
dairy purposes, 14-15%. White and Nichols (205) studied data from 
1,347 Holstein cows in Pennsylvania herds and found that the main 
reasons for disposal were: low production, sterility, udder trouble, 
and cows sold for dairy purposes, with percentages of 30.0, 17,0, 
13.5 and 7.9, respectively, 
j. On the contrary, in a comparison with the above mentioned studies, 

I Parker et al, (147) analyzed a special herd where no animals were culled 

j for low production. Reasons for disposal of Holstein and Jerseys were stud- 

ied. They found that 41.3% of the Holsteins and 21.3% of the Jerseys were 
considered non-breeders. The second largest percentage of disposal was 



--oft "--~ ■■-•"' -jTiW^pa-s-^Tl' r* -—■■=> M -f-. ■*^' * •t^xn-rtp'tpy.-i'"^' .-<1 —"-■-»■- -*-- ■■•.».' ji.-(to<T»t 



29 

due to udder troubles with 10. 5% and 9,6%, respect! vely, for the two 
breeds. Also, Evans et al, (77), using records of 6I5 Holstein cows 
from Louisiana State 'Uni vers i ty herd, found that the principal reason 
for disposal was sterility which accounted for 21,6%. Low production, 
mastitis and udder troubles, and cows sold for dairy purposes, were 
the other main causes, with disposal rates of 15.8, 12.7, and 8.0%, 
respectively. Breeding difficulty was also the major reason for 
disposal in the study carried out by Salazar (I67) on 1 ,72if cows from 
seven herds of the North Carolina Institutional Breeding Association. 
He found that about 32% of disposals were due to breeding difficulties, 
2if% to low production, 12% to dairy purposes and 18% to mastitis. 
Ragab and Asker (155) reported that of 557 Friesian heifers 
imported to Egypt, 2'-^,^/o were sold for low yield, low fertility and 
other reasons, and that 7.9% died. Narvaez (l^O) studied ^15 Jersey 
and Holstein cows under the humid conditions of Canal Zone, Panama, 
and reported that the three main reasons for disposal, including the 
two breeds, were feet and legs 21%, udder problems 36% and sterility 
23.1%. 

Sex Ratio and Tw inn [n_q_ Rate 

Johansson (99) summarized records of nearly a million births in 
cattle from temperate countries, and found that the percentage of 
twins in dairy cattle was 1,88 while in beef cattle it was O.'i'i-. The 
twinning rate in dairy breeds was reported by Johansson (99) to be 
3.3, 2.7, 1,8, and 1.0%, respectively, for Holstein, Brown Swiss, 
Ayrshire and Jersey. Similar results in the same dairy breeds have 
been indicated by Nalbandov (139). 

Asker and El-ltriby (I7) found that occurrence of twins among 



.MtWias MMi-llHl i rp ii ri ill i ■ » m. i ■ |i»,« l l ||| l Kiji aBBenaH 



30 

Friesian cattle in Egypt v/as ].8%, He reported a percentage of 0.8 
for local cows. 

Productio_n 

The low milk production of native cows and increasing demand 
for milk initiated the introduction of some European dairy breeds 
into countries of the tropical belt. These importations have presented 
researchers with the opportunity of studying responses of pure exotic 
breeds under local conditions as well as to investigate the influence 
of grading-up native cattle with these European breeds. 

Milk production of European dairy cattle in tropical areas is, 
in general, lower than that in temperate countries. The unsatisfactory 
milking performance of European breeds of dairy cattle in tropical 
regions has been explained by the direct effect of climate as well as 
by other environmental effects such as low plane of nutrition, diseases, 
and primitive management systems. 

The limited information available pertaining to performance of 
pure Holstein cattle in tropical areas shows that average milk yield 
is lower than that observed in temperate countries. Reported averages 
per lactation, from cows kept at experimental stations and governmental 
farms, range from 1,300 and 2,500 kg reported by Narvaez (l^-O). and 
Naufel (I/4I) from studies carried out in Panama and Brazil, respectively, 
to 3,700 and 3,900 kg reported by Mahadevan (125) and Hirsch and 
Schindler (93) from observations taken in Ceylon and Israel, respec- 
tively. 

Little information of performance of Holstein cattle at high 
altitudes of tropical countries has been found available in the liter- 
ature, Rom,an et al, (I63) studied production, records from th,e milk 



) 



31 

testing program of the Ecuadorian Holstein Association. Some h5 ,QQQ 
records grouped in four areas ranging from 2,250 to 3,100 meters in 
eievation and from ] 0° to 1 7°C were analyzed. Average milk and fat 
yields varied from 3,803 and 128 kg to 3,96^ and 142 kg, respectively, 
Wells et aU (203) from a small experimental herd situated at an 
altitude of 2,000 meters in Ethiopia reported an average of 4,983 kg 
in second lactations of pure Hoi steins. 

The highest national mi I k production average is the 5,900 kg 
reported by Rende] (157) for Israeli Friesians, This is compared 
with the 1966-67, DH!A (67) Holstein cows in the United States that 
produced an average of 5,800 kg of milk and 214 kg of butterfat, 

A lactation record is the result of two sets of factors, genetic 
and environmental. For purposes-of selection and breeding, it is 
Important to make accurate allowance for the one in order to arrive 
at a good estimate of the other. 

Leaving aside the variation due to feeding and management, which 
is without doubt large, there are several environmental factors 
affecting mFlk yield. Among them are year, month, age, length of 
record, days open, and previous dry period. 

Year of GaWjn^ 

Most studies carried out in temperate as well as in tropical 
zones Indicated that year of calving exerted considerable influence 
on variation of milk yield. This variation is influenced by the 
improvement of nutritional and managerial conditions that from year 
to year are practiced In many herds. However, the use of selection 
of Improved animals and culling systems affects also this variation. 

The USDA (I93) reported an Increase in average milk yield from 



mBi^^<ffT ^ 'gMii I' Ci.i ii'ni' j rj , ''"■■•—"*■"»—— --^^^'-' • ■ ■ ■ ■ -■■ - .f.^^.^ 



32 

4,508 ]b per cov\i in 1931 to 7,004 lb per covi in I960 for the United 
States as a v/hoie. A good example of long-term year influence is 
the significant effect on milk yield indicated by Wilcox and Young 
(209) in a population of Jersey cattle under the semi-tropical 
conditions of Florida. Yearly average yields were found to have 
increased steadily from 5,415 lb in 1932 to 9,070 lb in I96O, 

Month of Calving 

Month or season of calving is a factor of importance in herds 
where differences in production betv\'een different seasons of calving 
are considerable, A knowledge of the magnitude of variation according 
to time of calving aids in the analysis of cow records is used in 
preparing herd management programs. 

Extensive observations concerning the effect of month of calving 
on milk and fat production have been carried out in temperate 
countries. Woodward (210) found that DHIA cows of 12 states in U.S.A. 
which freshened in April, reached a higher peak of production than any 
other group. He concluded that cows calving in April were naturally 
at the high point of their lactation period in May or June, and these 
months were the most favorable for milk production. Bereskin and 
Freeman (26) investigated effects of month of calving in herds at 
three levels of production in Iowa. They found that the highest 
production was by cows calving between November and February; the 
effect of month was slightly different in the three levels of produc- 
tion. 

Very little information on the effect of month or season of 
calving on milk production is available from tropical countries. 
However, Clark (57), from a large volume of data on dairy cows in 



,33 

Queensland, Australia, published an extensive study covering the 

period iSkB to I96O, He observed that dairy cows that freshened in 
June and July produced 20% more milk and butterfat than those which 
calved in December, January or February, He also indicated that 
cows which calved in late winter and spring completed longer lacta- 
tions than those which calved during other periods. Similar results 
were reported by Naufe] (141) who analyzed 1,595 lactations of 
Holstein cows in Brazil in a period between I927-I963 and found that 
cows calving in fall and winter produced si gni f i cati vely more milk 
than those calving in other months, Bodisco et al, (32) found also 
highly significant differences in daily milk yield of Criollo dairy 
cows calving during the dry and rainy season in Venezuela. 

Conflicting results have been reported by other investigators in 
tropical zones, Mahadevan (125) observed that the variation in yield 
with month of calving was not significant in his study of European 
breeds, including Holsteins in Ceylon, Boyazoglu (37) in study of 
about 20,000 records of Friesian cows in South Africa indicated that 
season of calving was found to be less important as a source of 
variation in milk and fat yield than is generally accepted, Verde 
(199) observed variable results in his study with pure and cross- 
bred Holsteins in Venezuela, Magofke and Bodisco (121) also found 
that month of calving did not influence lactation yields of Criollo 
dairy cows in Venezuela. In support of these results are the findings 
of Kohli and Suri (111), Saxena and Kumar (I70) and Singh and Dutt 
(175) who in native breeds did not find an effect of month of calving 
on lactation yield. 



■ ■•?gta^t p i r i t i.i B <ll M|i| iWJ »l l 5Wi )-'« ff^tfCS > < i:^:a — ^^I « * ^ J A i K99Ui-!Vnf * nmmtti S-m eZS fSS^ ^j iM^ 



3k 

The age at which the cow freshens is one of the environmental 
factors affecting milk yield that has been more extensively studied. 
In genera], European dairy breeds in temperate regions reach a 
maximum production around the fifth lactation. However, maximum 
production of European breeds under tropical conditions is attained 
before the fifth lactation. For example, Mahadevan (125) found that 
the peak of production of five European dairy breeds in Ceylon was 
attained by the third lactation. He also indicated that this was 
probably due to the late age at first calving (40 months) and the 
long calving intervals {kSS days) these animals showed. Boyazoglu 
et al, (38) observed that maximum milk production in Ho] stein cows 
in South Africa was reached in the fourth lactation. 

The rate of increase in yield from first lactation to maturity 
is generally larger in European cattle under temperate conditions 
than those subjected to tropi ca| .condi tions. However, there are 
several studies in which intensively selected European breeds under 
good managerial practices in the tropics have shown increases which 
are comparable with those obtained in temperate areas. Mahadevan 
(125) found that yield of five European dairy breeds in Ceylon i n~ 
ci-eased witi-i age. These increases varied from !g to 32% and were 
considered to be similar to those obtained in Europe, Abdel-Ghani 
and Fahmy (I) from study of Holstein cows in Egypt reported an in- 
crease from first to fifth lactation of 27%, Also, Bodisco et a], 
(33) studying performance of Srown Swiss cows under the conditions 
of Venezuela indicated an increase of about 22% from first to fourth 
lactation. In a recent study Naufel (U;-]) revealed that there was an 



35 

increase in milk and fat yield up to the age of approximately six 
years in Ho] stein cows in Brazil, He also found that milk yield 
increased more than fat yield in later lactations. 

The average age at first calving for Holstein cows in temperate 
countries varies from 27 months as reported by Plum and Lush (151), 
to 3^ months observed by Towels (190), Salisbury and VanDemark (168) 
presented summary of data on age at first calving of dairy breeds as 
reported in England, Sweden, and United States, Mean age varied from 
27 to 33 months. Average age at last calving ranged from 59 months 
as indicated by White and Nichols (205) to 83 months found by Evans 
et al, (77). 

Many studies carried oufwith Holstein cattle under experimental 
conditions and tropical environments have shown that age at first 
calving is in the range observed in temperate countries. E|-ltriby 
and Asker (73) reported an average age at first calving of 3k months, 
in Holstein cows under experimental conditions of Egypt. Similar 
results were observed by Asker et al. (I9) from study in Irak. 
Boyazoglu et al. (38) from data on 3,000 registered elite Friesland 
cows representing 256 herds in South Africa found that age at first 
calving was 32 months, Hovjever, Mahadevan (125) in his study of 
European breeds in Ceylon reported an average age at first calving 
of ho months. 

One of the purposes of standardizing records for age is to 
facilitate comparison of records made by cows of different ages. 
However, one of the main objectives of using age correction factors 
is the removal of potential sources of bias in genetic studies. 
Johansson (97) estimated that age of the cow accounted for 10 to 30% 
of the intra-herd variation in milk yield per lactation period. Lush 



. -r=..*»>T. .^r^-^m..^ - , .. , , .., . „ _ 



36 
and Shrode (II9) stated that the general importance of age was ]h 
to 16% of the individual variance in unselected records. An impor- 
tant practical consequence of the use of age correction factors is 
in early progeny tests. However, most information related to age 
correction factors has been obtained from European breeds in temperate 
countries, and very few have been published from tropical areas. 
Mahadevan (126) indicated the incorrect practice of using correction 
factors for age published for European breeds to convert first 
lactations to maturity in tropical cattle. He stated that correction 
factors based on European data, when applied to Zebu stock, would 
tend to over correct first records and under correct records made 
at maturity. He emphasized that correction factors, wherever they 
are used, must be based on data to which tliey are applied. He in- 
dicated also that it might even be wiser, as Robertson (I60) has 
pointed out, to use no age correction at all on tropical cattle than 
to use inappropriate European factors. 

Age correction factors for European dairy cattle in temperate 
countries are presented in most of animal breeding and management 
texts. 

Length of Recor d 

Most purebred associations of dairy cattle have adopted SOS- 
day lactation periodjas a base to measure production. This standard 
has been chosen because, of the fact that a cow produces most profitably 
vjhen she calves annually. 

Most dairy cattle in temperate countries milk 305 days or more 
unless dried off by the manager. However, there is a great variation 
in lactation length of native cattle and European breeds under tropical 
conditions. 



37 

Averages of lactation lengths around 370 days in Ho! stein cows 
in Egypt, Arabian Republics, and Uganda were reported by E]-!triby 
and Asker (73), Asker et a], (18) and Marples and Trail (131), 
respectively. Asker et a1, (I9) also found an average of 322 days 
for Holstein cows in Iraq, and Boyazoglu (37) observed lactation 
records of 294 to 3OO days in Friesland cows in South Africa. Roman 
et al. (163) in a study of Ecuadorian Holsteins reported 28if days 
for records amputated at 305 days. 

The variation in lactation length of native cattle is considerable, 
Length ranges between 56 days in BON cattle in Colombia as reported 
by Pearson et al. {]kQ) , to 317 days Red Sindhi cows in India as 
indicated by Amble et al. (9). However, this variation has been 
also observed In European or crossbred cattle reared under the ~ - ' 
. conditions of management prevailing in tropical areas. Most reports 
concerning native and European dairy breeds in the tropics indicate 
a high correlation between total yield and lactation length. These 
correlations varied from O.k to 0.9 as reported by Mahadevan (126), 
and Naidu and Oesai (I38), respectively. 

Days Ope n 

The number of days a cow remains without becoming pregnant , after 
parturition can be defined as days open. This variable is important 
in herd management because it indicates the need for conception at a 
specific time after calving. 

Rice et al. (I58) concluded that with an average of 100 days 
open a 12 to I3 month calving interval would be maintained. Smith 
and Legates (I78) in a study of nine North Carolina herds reported 
mean values for days open of 143, 146, and 145 days for first, second 






38 

or later, and all lactations, respectively. Johnson et al. (102), 
by describing the use of Herd Reproductive Status method and its 
influence on dairy herd. found that the average days open In three 
herds (300 cows) from North Carolina was ]kQ days. After using the 
system, the number of days open decreased to 126 days in the first 
year and to 114 days in the second year. Barrantes (22) in a study 
of Jersey cows In Florida found that means for days open of heifers 
and cows were I76 and 162 days, respectively, and about 62% of 
records had from 70 to 110 days open. 

Rice et al. (158) indicated that pregnancy depressed yield 
particularly after I50 days of gestation. This variable may be 
measured practically either as days carried calf or days open from 
parturition to conception. They also indicated that both of these 
measures are superior to calving interval in that they permit the 
inclusion of information on the final lactation of cows. They 
finally concluded that, even in extrem.ely well-managed herds, days 
open could have an important effect on milk yield. 

Smith and Legates (178) studied the relationships between days 
open and 90-day and 305-day production using 4,385 lactation records 
from 9 North Carolina institutional. Herds. Relationships were studied 
separately for first, second or later, and all lactation to determine 
if adjustment of 305-day lactation records for days open was warranted 
in compiling sire summaries. They found that days open during lacta- 
tion significantly influenced production and accounted for 6.5, 4.3 
and 4.2% of the variation in 305-day milk yield for first, second or 
later, and al] lactations, respectively. Etgen (76) found that milk 
and butterfat yields increased as the number of days open increased, 



^ =^ssS3Q<caBMMU«M 



39 

and the increase was least in the 2-year old and greatest in the h~ 

year old cows, Spalding (180) indicated correlations between days 
open and milk yield to be 0.22 and 0.20, respectively. He also 
observed that 100 days open compared with Gk days as standard increas- 
ed mi Ik yield by 1,1/0 lb. 

No reported information concerned with the effects of days open 
on milk yield of cattle under tropical conditions was available in 
the literature so that a comparison with results in temperate 
countries could be made. 

Previous D.r_y._ .Pe.rXod 

The interval of timiC a cow remains dry between the end of a 
lactation and the beginning of the next (the one being studied)' is 
called previous dry period. 

Studies carried out on data from European dairy breeds in 
temperate countries have indicated that the optimum length of dry 
period is near 60 days. However, ranges from k7. to 56 days were 
reported by Johansson and Rendel (100) in Swedish dairy breeds. 

As pointed out by Rice et al. (I58), the number of days dry 
prior to calving does not greatly Influence lactation yields unless 
the dry period is quite short, e,g,,30 days or less. Several authors 
(15, 23, 1^9, 169) have indicated that a definite decline in production 
occurs with dry periods of less than hO days. Klein and Woodward (108) 
from a group of about 15,000 lactations representing 12 states in 
U.S.A. found that cows dry 1-2 months gave 9,2% more milk than when 
dry 0-1 month, Spalding (I80) found that a 50-day dry period was 
associated with an increase in milk pi-oduction of 1,050 lb when 
compared with no dry period, but that there was little to be gained 



with dry periods of over 50 days in length. Swanson (183) studied 
five pairs of identical twins and found tte t the twins with no dry 
periods produced 26% less k% FCM in the second lactation than their 
mates which had a 6Q-day dry period. 

!n general, it has been observed that lengths of dry periods 
among European dairy cows under tropica! conditions are quite variable. 
In most cases these intervals are longer than those found in temperate 
cattle. Previous dry periods varying from 9^ to ]k] days have been 
reported from studies with Kolstein cattle under different tropica] 
regions. E]-ltriby and Asker (73) reported an interval of 9^ days 
for Holstein cows In Egypt. Narvaez (140) found previous dry periods 
of 99 days in Holstein cows born in Panama and 126 days for those 
imported to the country. Asker and El-ltriby (I7) observed previous 
dry periods of 103 days in Holstein cows under the conditions of 
Egypt, .and Mahadevan (125) indicated an average of 1 35 days for dry 
periods of European dairy cattle in Ceylon. Pure Holstein cows In 
Venezuela had a previous dry period of l4l days as reported by Verde 
(199). He found no significant effect of previous dry period on 
milk yield in a mixed population of cattle In Venezuela. 

Also, differences in lengths of dry periods have been observed 
from studies of native cattle in tropical areas. Reported averages 
varied from 116 days observed by Magofke et al. (122) from a study 
of milking Crlollo cows in Costa Rica, to 2^0 days reported by 
Mahadevan (126) for Red Sindhi and Kangayaman cattle in India. This 
last author concluded that the between-hard variations in dry period 
were largely attributable to differences in management. 



Heri tabi I i ty_ 

Some causes of variation in milk yield due to environmental 
effects have been mentioned already. From observation of these 
environmental effects, it is apparent that milk production is a 
highly modifiable trait. However, in the study of causes of variation 
in milk production, genetic effects must also be considered. 

The relative effect of environment and heredity on the variation 
in milk production can be estimated by using adequate statistical 
procedures. Several investigators have emphasized the importance of 
estimating heri tab i 1 i ti es in order that the breeder can make better 
use of selection systems in the improvement of characters of economic 
importance. 

Johansson and Rendel (lOO) summarized the results of heri tabi lity 
studies on milk and butterfat production that have been carried out 
on data from recording associations in several countries and from 
different breeds. They indicated that, in general, practically the 
same value of heritability is obtained by using butterfat yield as 
milk yield vjhen based on comparable records, usually the first 305 
days of the lactation. Values of her i tabi 1 i ties for milk or butterfat 
yield vary from 0.27 in Dutch Friesians to 0,if3 in six British dairy 
breeds. Trie observed value for Holstsin Friesians In U.S.A. v.'as 0,27 
as found by Tabler and Touchberry (I85). However, a high value of ■ 
heritability of O.76 was reported by Gur" Yanava (88) from study of 
Latvian Red cows and Jersey crosses in Russia. Johansson and Rendel 
(100) from investigations carried out using data from Danish bull 
testing stations reported relatively high heritability values averag- 
ing near 0.6. in order to explain the high value obtained, several 



kz 

hypotheses were formulated. it was agreed that particular environ- 
mental differences have made themselves apparent even between the 
progeny groups tested at the same time at the same station, so that 
the heritability estimate was thereby inflated to a certain extent. 
It was also explained that the heritability figures were higher at 
the testing stations than on the farms due partly to greater effi- 
ciency in recording and better adjustm.ent of the feeding to the 
individual nutrient requirements, and partly due to the contempora- 
neity within and between groups at the same station. 

Biased estimates of heritability resulting from incorrect 
methods of estimating components of variance have been reported by 
Farthing and Steele (80), They give an example by using three popular 
methods of analyzing data of milk yield, and concluded that the model 
which Includes sire, dam/sire, cow/dam/sire, and within cow will give an 
unbiased estimate of heritability. 

Studies of heritability of milk yield for European and native 
cattle have been conducted in tropical environments. Mahadevan (126) 
indicated that one of the main objects in estimating the heritability 
of a character in a tropical environment as distinct from a temperate 
environment is to determine whether or not the genetic expression of 
the character is different, in the two environments. He also indicated 
that studies of the heritability of milk yield at different environ- 
mental levels within temperate countries have been quite contradictory. 
Studies by Johansson (98), Korman (112), and Gravert (85) reported 
heritabilities to be higher in high producing than in low producing 
herds, while in other studies, such as in those conducted by Gravert 
(86), Burnside and Rennie {k6) and Van VIeck and Bradford (I96), no 






43 

increase in heritability vjas observed with increase in production 
level. Mahadevan (126) concluded that it may be that very extreme 
environmental differences are necessary before they affect herita- 
bility. He also stated that unfortunately heritability studies 
conducted in tropical countries have been based on a relatively small 
number of animals and therefore lack accuracy for purposes of com- 
parison with corresponding estimates from temperate environments. 

Heritability values for milk yield estimated from native breeds 
under tropical conditions have been reported to vary from 0,13 for 
the Kankrej breed of India as reported by Amble et al. (7) to 0,71 
observed in milking Criollo cattle in Venezuela indicated by Magofke 
and Bodisco (121). 

Estimates of heritability for milk yield from purebred European 
dairy breeds under tropical conditions show a range from 0.18 ob- 
served by Mahadevan (125) in Ceylon to 0.55 reported by Naufel (l^rl) 
from a study of Holstein cattle in Brazil. 

A number of studies on heritability of milk yield in crossbred 
dairy cattle from tropical areas have been reported. Values of 0.47, 
0.23, 0.19 and 0.21 were indicated by Okumu and Berry (146), Singh 
and Desal ( 1 74) , Mahadevan (124) and Verde (99), respectively, from 
studies conducted in East Africa, India, and Venezuela. 

Repeatabi 1 i ty 

The correlation between performance in different lactations of 
the same animal, often given the name of repeatability, is one of the 
important measurements in the analysis of milk production. Repeat- 
ability refers to the average correlations over a series of lactations 






and can be considered as the proportion of the total variance due to 
differences between cows which persist over all lactations concerned. 

Estimates of repeatability for Ho] steins under temperate condi- 
tions are within the range of 0,^2 as reported by Gacula et al, (83) 
to 0.52 as indicated by Deaton and McGilliard (63), Repea tabi 1 i ties 
of records expressed as deviations from herd--year-season averages 
were reported by Bereskin and Freeman (2/) to be O.5O and 0.^7 in a 
study of Holstein cattle in Iowa. 

Repeatability of records by native cattle under tropical con- 
ditions has varied from 0.^6 as reported by Mahadevan et a], (127) 
for Boran and Jiddu cattle in East Africa to 0,70 as estimated by 
Mahadevan and Marples (128) for Nganda cows also from East Africa. 
Mahadevan (12^) indicated that repeatability of milk yield from 
crossbred indigenous-European cows in the tropics is of the order 
of 0,5, He found repea tab i 1 i ti es of 0,58, 0.55, 0,65 and O.^lO in 
study of crosses between European and Indian breeds. 

Repeatability studies of European dairy cattle in tropical con- 
ditions have varied from 0,31 found by Magofke and Bodisco (121) in 
Brown Swiss cows in Venezuela, to 0,65 reported by Hofmeyer and 
Boyazoglu (95) in Jersey cows in South Africa. Naufe] (I4l) obtained 
value of 0.36 for milk yield and Q.^tl for fat yield in Holstein cows 
in Brazil. Seller et al. (179) reported that repeatability estimates 
based on the pooled within herd-year correlation of first and second 
lactations for 1,728 Friesian cows in Israel ranged between 0,^8 and 
0,60, 

hl£^^..ky..^.3JS3 ! nteract ion 

Artificial insemination with dairy cows is used not only in 






45 

temperate countries but is also being widely accepted in tropical 
areas. The improvement of many dairy herds in the tropical belt to 
a great extent depends upon importation of proved sires from the 
more developed countries. Specifically, Latin American dairy cattle- 
men have been purchasing semen from dairy bulls tested mostly in the 
United States, Semen from these bulls has been used in different 
regions of Latin American countries v-jhich are characterized by a 
wide variation in topographic as well as climatic conditions, A 
great deal of variation in management and feeding systems for dairy 
cattle is typical of these countries while more uniformity of general 
feeding and m.anagement conditions is observed in the United States, 

Commercial breeding organizations operate with bulls that in 
most cases come from we] 1 -managed herds, and have been evaluated on 
their daughters' performance which in general has been submitted to 
better than average managerial practices. Daughters of these bulls, 
through artificial insemination, will be spread to widely diverse 
environmental conditions which are still more variable in tropical 
areas and in general will be far from the favorable conditions that 
prevailed for the daughters used originally to evaluate the sire. 

Since the use of artificial insemination is highly developed in 
dairy cattle, scientific studies in temperate countries have been 
conducted with the purpose of measuring the importance of interactions 
between sires and the herds in which they have progeny. Unfortunately, 
information on this topic from tropical areas as far as is known is 
not available in the literature, , 

Some 3,900 first lactation records from daughters of 126 sires 
in 1,094 herds were studied by Hickman and Henderson (92). They found 



k6 

that the fraction of total variance due to herd by sire interaction 
was oniy 2% for milk and fat yield. Legates et al. (11 7) analyzed 
production records of 25,000 daughters of Guernsey, Hoi stein and 
Jersey sires used in artificial breeding associations throughout 
the United States. The percentages of intra-state total variances 
for milk and fat production due to herd by sire interactions were 
zero for Guernseys and Jersey and 2.1 and 1.2% for Holsteins. From 
results obtained in this study they finally stated that specific 
sires by herd differences were not of major importance and that the 
ranking of a group of bulls based on their daughters' performance in 
a given herd would be expected to be substantially the same as for 
the same bulls compared on basis of daughter performance in other 
herds in the same state. Mason and Robertson (133) studied milk 
records from 13,000 cows bred artificially in Denmark with herds 
divided into three groups according to production. They did not 
find evidence of any sire-herd interactions for yield, either within 
or between management levels. The true ranking of bulls for breeding 
value was apparently the same at all levels. From data of daughters 
of ifl5 Red Danish Milkrace sires tested at Danish bull testing 
stations and farm.er herds, Touchberry et al. (I89) indicated that 
tne interaction between sires and herds was small. m herd by sire 
interactions were noted by Wadell and McGilliard (201) from a study 
with daughters of Holstein, Jersey, and Guernsey bulls from both 
artificial and natural breeding in Michigan. Van Vleck et al, (I97) 
estimated components of variance from records of artificially sired 
Holstein cows in New York State. They found that sire by herd and 
sire by year-season components were very small (1-2%, and 0%, respect- 



.'^ ~"T~'" Ti I rnr' . - iii TiM i i iri i in i r iiiTfinriii ii— iiii tti" 



ively) indicating little genetic by environment interaction in dairy 
records under New York conditions. 

No interactions of practical importance between sires and herds 
were reported by Burdic!< and McGilliard ('45) from a study of Michigan 
DH!A Hoi stein and Guernsey herds. About h% of the total variation 
for milk and fat yield in Hoi stein herds was due to herd by sire 
interaction and 2 and 0%, respecti ve 1 y ,for Guernseys. In a recently 
published study, Mao and Burnside (I30) found no interaction of 
importance between sire proofs and herd environments when herds were 
grouped according to ten environmental factors. However, a highly 
significant interaction involving sire proofs and level of grain 
feeding in summer was found, suggesting that sires ranked differently 
on the basis of progeny fed relatively high levels of grain versus 
low levels. 

Correlations between sire evaluations at different herdmate 
levels have been studied by several investigators. in most studies 
these correlations have been high, suggesting that progeny groups 
tend to rank similarly under different herd environments, Robertson 
et al, (161) studied data from England, Wales and Scotland, Estimated 
correlations between breeding values for yield at three levels of 
production were close to one. it was concluded from these results 
that there was no need to concentrate progeny testing in higher 
producing herds and that daughter records from all herds, irrespective 
of level of production, can be used with equal confidence. Genetic 
correlations in this study ranged from 0,83 to O.96 among sire progeny 
groups at the three levels. High genetic correlations betvjeen evalua- 
tion of sires in four different environmental levels were also reported 



\ 



^ n-ik\Tj f rw ^ t mmftig) u jm Mar ^ Mrru 1 tf T im m in mM^i iu ,'i 



^■8 
by Van Vleck (195) from a study in New York State, He concluded 
that since the genetic correlations were near unity between evalua- 
tions at different environmental levels, the evaluation of sires 
would be nearly the same in all herd levels, McDanie] and Corley 
(135) investigated relationships between independent measures of 
the breeding value of a bull at different levels of herd production. 
They found that correlations among sire progeny averages at different 
herd mate levels were all very high (0,88 to 0,96) and indicated 
that bulls ranked in about the same order at all levels. However, 
contrary evidence has been presented by Bereskin and Lush (28) 
who indicated that summaries on bulls in high level herds might not 
be very indicative of their performance in low level herds. 

With the purpose of investigating whether genotype by region 
interactions were important in ranking bulls, Lytton and Legates 
(120) utilized the first available DH!A record of 10,5^1-8 artiPicially 
sired daughters of 46 Holstein sires used, in the northern and 
southern regions of United States, Correlations between the average 
breeding values of sires in the two regions for milk, fat yield and 
fat test approached 1,00, Estimates of sire by region interaction 
variances for the three traits were essentially zero. These results 
suggested that influences associated with a particular region should 
not confuse the ranking of sires in different regions. 



■**fHl^t«!»9Il^ 



MATERIALS AND METHODS 

P.§.s,^Q..PiLon-Of. .l^He Herds 

Records of Kojstein cows from three herds, belonging to the 
Colombian Agricultural Institute ( I CA) , for the period I956-I967, 
v^fere the source of data for this study. 

The foundation stock of these herds consisted of groups of pure 
Colombian Holstein cattle, and of Holstein groups imported either 
from Holland (Herd 1 ) , or from United States. Some importations of 
heifers from United States have been made in more recent years« 
Purchases of semen from proved sires from United States have been 
frequently made, and since I96O semen of these bulls has been used 
conti nuously. 

The three herds are located at three experimental stations 
situated in distinctly different climatic and topographic conditions 
of Colombia. Table 1 shows some details of the situation and prevail- 
ing climatic conditions for the three stations. 

Stations 1 and 3 are situated at high altitudes but with different 
topographic conditions. Station 1 i s on a pla teau . cal 1 ed Sabana de 
BouoLa, wliii^h is located at tlie Central part of Colombia. The land 
is completely arable with highly favorable climatic conditions for 
cattle and an ability to produce good quality pasture and grains for 
silage. Pastures prevailing in the station are Kikuyu (J^Jlisejium 
cJAi?Ji5.lLiilu.[n) , Ryegrass (j-^oJIym pexetinjs) , Orchard grass (O^ac t_yj i_s 



^9 



50 



Table 1. Situation and climatic conditions of the three experimental 
s tat i ons stud ied. ' 



Station I 
(Herd 1) 



Sn,< n 



mm 



13.1°C 
19.5°C 



station 2 
(Herd 2) 



Altitude (mts above 

sea level) 2,550 mts 

Latitude 1+° 42' N, 

Longitude 7^+° 12' W. 

Average annua 1 ra i nf a 1 1 

Average annual temperature 

Maximum Media 

Mi nimum Media 
Average Relative Humidity 72% 



1 ,006 mts 
f 32' N, 
76° 17' W. 
879.3 nim 



23.7°C 
29.8°C 



17.8°C 

72% 



Station 3 
(Herd 3) 



2,528 mts 
1° 13' N. 

77° 16' W. 

1 ,226.5 mm 

13.9°C 

17.39°C 
8.30°C 

74. 7% 



From Bole tin Meterologico (36), 



.9jo.[I!fj:iLtil) . i^ed Clover OlnloLL^O] .PJ:£i£n_se) and V/hite Clover 
(Illf£lJiirn £e£_ens ) . Most of the silage produced to feed the cattle 
comes from oats (Avena JiLy.:va) , and corn. 

The topograjDhy of Station 3 is qui te di f ferent from that of 
Station 1. it is located at the south of Colombia. The terrain is 
inclined with a low proportion of arable crops. However, after hard 
work in the early years, the establishment of improved pastures has 
been quite successful. Pastures and silage prevailing at the station 
are the same mentioned for Station 1. 

Station 2 has considerably different climate. it is situated 
in the southwest part of Colombia, in a very rich valley located at 
an altitude oF about 1,600 mts lower than that of the other two 
stations. The mean daily temperature is about 1 o'^C higher than those 
temperatures in Stations 1 and 3. The station has complete arable 
acreage with a higher favorable environment to produce improved 
pastures for hot climates, and grains for silage. The main pastures 
prevailing are Pangola grass ( 01g.Lt:^ir ij. .di2£yij.bet2S ) and Paragrass 
(faaJ.iLynKiL^.azyi:ascens ) , and the silage produced to feed the cattle 
is basically made from corn, 

it can be observed that climatic conditions under which Herds 1 
and 3 are living, though differing in a number of respects from 
conditions in temperate countries, are quite favorable to the well 
being of these herds. On the other hand, Herd 2 has been reared 
under true tropical conditions, with more adverse climatic effects. 

All three herds have been maintained on a moderately high plane 
of nutrition, though in early years conditions were not so satisfactory. 
The three herds are on pasture around the year and access to silage is 



52 
permitted. Furthermore, all milking animals are fed concentrates 
according to production. The principal components of the concentrate 
ration are corn meal, cottonseed meal, wheat meal, soybean mea] , 
sugarcane molasses, mineral mixture, and salt. 

Until 1959 cows in all three herds were milked by hand. Since 
i960, cows in Herds 1 and 2 are milked mechanically, while those in 
Herd 3 are still mi Iked. by hand. 

j}at_a 

Records in this study were divided in two different groups. One 
group consisted of information related with reproductive performance. 
The second group concerned with milk production of the three herds. 
The total number of records analyzed for reproductive performance 
consisted of normal gestations. No aborted records v.-ere included in 
this data, and records with calving intervals longer than 730 days 
and gestation lengths shorter than 250 days v^-ere eliminated. 

Production data consisted of 2X , 3C5--days, or less, complete 
lactation records. Records with less than I50 days vjere not included, 

fhe following information was taken into account for each gesta- 
tion studied: 

(1) Station number. 

(2) Animal number. 

V 3y Bi'eed o i aii I ma 1 , 

{h) Si re number. 

(5) Breed of si re, 

(6) Dam number. 

(7) Breed of dam, 

(8) Bi rth date. 



■-,: - - ■—- 



53 

(9) Gestation number. 

(10) Date of last parturition, 

(11) Date of fi rst heat, 

(12) Date of first service, 

(13) Date of conception. 
( 1^) Conception bul ] . 

(15) Breed of conception bull, 

(16) Services per conception, 

(17) Date of parturi tion, 

(18) Sex and defect of calf, 

(19) Birth weight of calf, 

(20) Reproductive disorder. 

(21) Cause of end of record, 

!n addition to the information referred in numbers (l) to (8) 
above, the following information was considered for each one of the 
lactations studied, 

(9) Lactation number, 

(10) Date of parturition. 

(11) Age at parturi tion. 

(12) Days dry before this parturition, 

(13) Length of lactation, 
( ]h) Mi 1 k production. 

(15) Fat percentage. 

( 16) Mi Ik fat production. 

(17) Cause of end of lactation. 

(18) Conditions affecting lactation. 

(19) Date of pregnancy during lactation. 



^* 6 ^ii ffi' ^ 7r^H ' g> r :» ^wi ns rMms^i Hj^S i fi t rs' t nKam m 



54 

Records were punched into IBM cards. Card layouts are shown in 
Appendix Tables 31 and 32. For reproduction data each card repre- 
sented one gestation' of a cow. For production data each card repre- 
sented a single lactation record of a cow, 

■S_tat istical Proc edures 
Ag-gJ'Muc t i on da t a 

All analyses for reproduction data were performed using the 
Texas General Matrix Program, of which least-squares is the major 
analytical technique. Data were analyzed separately for each herd. 

The responses included in the mode] were: calving interval, 
calving date to first heat, first heat to first service, first service 
to conception, services per conception (original and transformed'* 
gestation length, and birth weight. In the case of the first three 
responses already mentioned the analyses were based on the same set 
of data. A variable number of records were used for the five other 
responses, according to the availability of the data. 

Independent variables considered in these analyses were: year 
of freshening, month of freshening, sire of cow, and age of cow (linear 
and quadratic). However, month of freshening was not included for the 
responses first service to conception, services per conception 
(original and transformed), and gestation length. Independent vari- 
a^.cs ,or response birth weight were the same five considered for the 
three first responses but sex and gestation length (linear and quadrat- 
ic) were also included in the model. Any cow having a gestation 
length of less than 250 days or greater than 300 days was not included 
In these analyses. No limitations vjere placed on either age or birth 
we i g h t , 



•" nr'igm ■ ii i i iiMiii «i iiiiirii n i« i ii i iii i i r imii m iiii nw ii 



55 



Tvjo analyses of services per conception were carried out. The 
first one v;as based on the actual services per conception. For the 
second analysis a transformation of the dependent variable was used. 
In this case the square root transformation was employed. This 
transformation was performed due to the fact that the number of 
services per conception does not follow a normal distribution, 

Intra-herd heri tabi 1 i ties for the eight responses studied were 
calculated by using the least-squares estimators for components of 
variance and based on the ratio of four times the variance of sires 
divided by the total variance. The i n tra-class correlation among 
paternal half-sibs was multiplied by four since the sire component 
of variance is expected to contain only one-fourth of the additive 
genetic variance plus a small portion of the epistatic variance. 
Then heri tabi 1 icy was estimated in accord with the formula: 

, 2 '^ cL 



, , 2 . 2 

where the O' g is the sire component and O" |^ is the mean square for 

remai nder. 

Variance of sires was estimated by the ratio 



MS 



MS 



where MSg - Mean square, of sires 

MS^^^ = Mean square of remainder 
and !< vias calculated b^' the formula 



K = 



(n. 



in whi ch S 



> 



t.„ n , 



n. 



^__) 



S - 1 
number of s i res 

number of observations in the i *-'"' sire 

total number of observations 



th 



56 
In calculating the standard errors of the heritability estimates, 
the formula given by Swiger et al, ( 1 84) was used. 




SE (h^) S-z^ \ / __2_ln^„~l_l_j[ln:..tl [L_±_iJ<:illtl 



K (n.-S) (S~l) 



where n, - total number of observations: 
and t = the intra-class correlation 



t ^ 



S 



o'l ^ al 



Pooled her 1 tabi 1 i t i es , considering data of the three herds to- 
gether, were calculated according to the formula: 



h pooled = 



(^S, -f O'S^ + O'S^) + {^K^ + C7^^ ^^-'^Rj) 



wnere ; 



.2 



.2 - 2 2 

^*S '^S^, ^S = a" Sires in Herds 1, 2_^and 3, 

respectively. 



2 2 2 2 

■^ R "R ^^R = 0° Remainder in Herds 1, 2, and 3, 

respectively. 

In calculating standard errors of pooled heritability estimates, 
the follo'wing formula was used: 






SE (h^ pooled) ="A-\ 



2 (n. -i) (1-t)^ [l ^- (1<-I)tj^ 

2 
K (n,"S) (S~l) 



57 

where: n. = n. in Herd 1 + n. in Herd 2 + n. in Herd 3 

al al al 

^ 1+2+3 



'23 1^3 

K pooled = a vjeighted average of K's where weights are the degrees 
of freedom for sires. 

a 
^.. (S. - 1) K 

K pooled = i = 1 ' i 



L_ (s - 1) 

i = 1 i 



where: a - number of herds. 

S. = number of sires in the i^ herd. 

K, = wi thin-herd K value. 
I 

Product i Qn_d3j: a_ 

Data were analyzed by least-squares techniques or by analysis 
of variance of adjusted data. In these analyses, the following types 
of records were removed: (l) records involving a sire with only a 
single record; (2) records with length of less than 150 days; (3) 
records with one or more observed values missing, and (k) records 
with one or more observed or computed values outside of biologically 
possible 1 imi ts . 

As with the reproductive data, separate analyses v/ere carried 
out for each one of the three herds. For each herd three different 
groups of records were considered. Group 1 included only first calf 
heifer data v.'hereas group two considered information on older cows. 
In group 3 the analysis was based on all available records. 

Dependent variables included in the model were: milk yield, 



58 

Fat yield and k% fat corrected milk (^-% FCM) , The formula used to 
convert milk yield to i(-% FCH was that suggested by Gaines (8'4) : 

k% FCM = 0.'+ total milk + 15 total fat 

For each analysis the same set of independent variables were 
used. These were year, month and sire. For analysis of first calf 
heifers, years were grouped together as follows: 

Years included 



Year group H?-I.d.J. .tLSIi!.! hSfJ^. 

1 55-60 55-57 59 

2 61-62 58™59 60 



Herd 2 


55" 


-57 


58-59 


60- 


-SI 


62- 


■63 


64" 


■65 


66- 


-67 



3 63-64 60-61 61 

^ 65-66 62-63 62 

5 64-65 63 

6 66-67 64 

7 65 

8 66 

9 67 



Covariates included were linear and quadratic cornponents for 
age at parturition, length of record and days open. For mature cows, 
linear and quadratic components associated with previous dry period 
were also included, whereas in the analysis of Group 3 data, the 
cubic component of age was added. To improve the inverse, the 
covariates were adjusted by subtracting constants as follows: 

UOl is. tcJtl t.S 



C.oya_r|_a_te Fj/s t ca 1 f he i_fej;_s Maiiira^cows Al I cows 

Age 36 70 70 

Length of record (LOR) 280 . 280 280 

Days open (DO) 120 120 i 20 

Previous dry period (POP) - ] 20 



, 59 
Age correction factors were estimated from the regression 
equations. Age of niaxiinum production calculated from the partial 
derivatives from prediction equations were 90, 87, and 93 months for 
Herds 1, 2, and 3, respectively, 

Intra-herd and pooled her i tabi 1 i ties for milk yield, fat yield, 
and 4% FCM were calculated by using the same formulas employed in 
estimation of her i tabi 1 i ti es for reproduction data. 

Nested analyses of variance for each herd were performed based 
on records of the group in which all cows were considered. The ' 
records were adjusted for all significant effects except sire. The 
adjustment was based on information previously obtained from the 
least-squares analysis carried out with all cows. Age was adjusted 
to 90 months, while length of record was adjusted to 300 days. 
These analyses were designed to estimate sire, cows in sire, and 
among records in cow in sire components of variation. 

Estimates of heritability and repeatability were also obtained 
from these analyses, intra-herd heri tabi 1 i ties for the three responses 
studied were calculated by using the following formula: 

h^ . k O'l 



o'i ^ o'l +a\5 



where ^ S is the sire component 



o 



^ C is the cow component 

a ^ ■ 

- W is the vjjthin cow component 

Variance within (^^W) - MS 

W 

-: 2 

Variance of cows (<-'^ C) was estimated by the ratio 



^yi*tiHfci;rii:iH' . 



60 



where MS„ - mean squares of cows 

MS^ = mean squares of within 
Kj = number of progeny per cow 

Because the unequal numbers in these data the coefficient K, was 
calculated by the formula: * ■ . ■ 

• ' • • .' ^ .. . _ 



C'^v 



Kj = ' "i 



D-S or d.f. for cows 



where n,, = total number of records 

n. . = number of records per cow 

n. = number of progeny per sire 

C = number of cows 

S = number of si res 

Variance of sire (f?s) was estimated by the ratio: 

■"' s = ^s .^; I; w + 2 " c )_ 

3 
where MS = mean squares of sire 

Kp ~ number of progeny per cow 
K = number of progeny per sire 

K was calculated by the formula: 



61 



-^ i !i_. " .] i 11 

n. n.. 



^ - 



S " 1 or d, f , for si re 



K was calculated by the formula: 



2 

:§! n 

n . . " ^L,, . J_; 

K = ____ n . . 



S - I 



in calculating the standard error of her i tabi 1 i ties the modified 
formula of Dickerson (68) was used. 



s. E. (h^ == "^ V va^- i^'h 



S' 



^^S 'i- C>'c .J. fJw 



where: var {(^1) = _J_ ( J^!s_ -^ _^^i_ _ \ 

"j^2 \ S -I- ] C-S + T ) 

Estimates of pooled he r i tabi 1 i t i es including data of the three 
herds together v^ere calculated by using the formula as follows: 



h poo 1 ed = 

-z 






2 

where: -^ Sj ^ 3 is the sum of the sire variances in Herds 1, 

2, and 3, Repeatabi 1 i ties were calculated by a similar approach. 



a t ' , » j f ^a'ggwg-'^'^c— ga 



62 

Standard errors of pooled herl tabi 1 i t ies were estimated by 

using the formula of Dickerson (68) already mentioned. However, In 

2 
the calculating K_^ value to estimate var (^S) a pooled K value was 

obtained by using same procedure performed in estimation of pooled 

K for reproduction data. Values for MS and MS used In the calcu- 

S C 
2 
latlon of var [Os) were the summation of mean squares for sires 

obtained In each herd and llkev;ise for mean squares values of cows. 

The number of sires and cows used in the formula were also obtained 

by adding sires and cows in each one of the herds and to this value 

a one or two was added according to the formula. 

Repeatability estimates for milk yield, fat yield and k% FCM 

were calculated from this set of data by using the formula Indicated 

by Becker (24) . 



ol 



2 2 



wine re: W = MS 



wi thin 
C = among cows variance 



cj2 

and C = MS- MS 

L — W 



K 
1 

K value was calculated by formula previously Indicated. 
Standard errors of repeatabi 1 i t Ies v;ere estimated by the formula 
presented by Becker {ik) . 

2 2 

2 (m. -1) (1 - R) r 1 + (K -1)^ 
S.E. (R) ^ \ L 1-1 



Kj (m. - N) (N - 1) 



63 

where m. - total number of observations 

R - repeatability value 
N = number of cows 

Pooled repeatabi 1 i ties estimates were calculated by using same 
technique to calculate pooled her i tabi 1 i t i es. !n this case the 
formula employed v^as as follows: 

2 

R =:: 1)2,3 

pooled -" 



(<^"" 1,2.3) * C^^' 1,2,3' 



.2 2 2 7 

where 0\j = O" w 1 n Herd 1 + C5"w jn Herd 2 + ^""w 

' '^ in' Herd 3 

2 ,.2 2 

and ®] ? ■? " C5' error i.n Herd 1 + O'error in Herd 2 

r%- 2 

+ U error in Herd 3 



!n estimating standard errors for pooled repeatabi 1 i ties the 
following formula was utilized; 



S.E. (R pooled) ^ 2 G?:m. - 1) (] -^ R,,)' [j .-(K H)R,1 



2 



K (£m. ~2:n) (rN-l) 
P 

where: L,m. = sum of total numbers of observations in Herd 
I , 2, and 3 

R = pooled repeatability value 

''— N - sum of total number of cows in Herd 1, ?., and 3 

1< - pooled K value, obtained by using the formula 
previously presented 



A further analysis was designed to estimate herd by sire intei-- 
action, using ^•56 records from 203 daughters of 20 different sires 



miMssmm t Vtw-^mr» lm r»i =>BSiimB, t\r ji. i »^ ii | ii il i ■■ ,,.r~t'»rr-T- CT!!MB8»»tt««»» .«l i« » i i fli iiii t »» 



6^ 

used in artificial insemination as well as in natural service in the 
three herds. Data included v.-ere the adjusted responses. Adjustment 
was based on the least-squares coefficients estimated in the analysis 
of the group of all cows. Included in the analysis were only those 
sires with daughters in two or more herds. 

Independent variables taken into account In the model were: 
herd, sire, and herd by sire interaction. The variable herd was 
considered as fixed. Dependent variables were the same considered 
in the analysis of the group of all cows and previously mentioned. 

Values for the components of variance associated with herd, sire, 
and herd by sire differences were calculated. The corresponding 
percentage which each component comprises of the total Intra-herd 
variance was also estimated. 

In the calculation of components of variance and percentages of 
the total variance the following expected mean squares were used: 

Source 

Herd (fixed) 

Sire (random) 



E(MS) 
2 






Herd x si re 
Remal nder 



2 2 

O MS + K •'> H 

2 .2 ^ 

R -h K O S 

,2 ^ 2 

Or + K 01-15 

2 

Or 



where ; 



U 



R - MS. 



O'hs ^ 



MS 



HS 



MS 



and 



HS- 



(n.. -^ 



i J 



n, 



nij 



r— L-ri 1.1 ^ ITtt rfc**!!* 



^^T^T^^gWfpfnW ill ■ ^^* i ""^*^^'ry* »^^r*^f^>M ■ 



where ; 



65 



HS 
n, , 



n 



U 



= number of herd x sire filled cells 
= number of observations 

- number of observations in the i i 

,, . th . 
the J s I re 



; rd from 



™ 7 



MS MS 

S ~ R 



and 



(n. 



2 

nj 



S") 



n, , 



vjhere: S = number of sires 



nj 



th „, 



number of observations in the j '^" sire 



-^2 



M'^ 



MS 



HS 



and 



3 H-1 



(n. 



i 



ni 



where: H = number of herds 

n = number of observations in the i ^'^ herd 

The percentage of total variance accounted for each one of the 
components was estimated by the formula; 



Percentage of total variance 



O' 



a 



2 

total 



66 



.-. 2 ,^ 2 2 2 
where: ^-^ Total = '"^ H + -'' S + ^T ^^3 ^ CJj 



and: O' j = ^^ H or ^-' S or ^Ti^g 

For comparison percentages of tot:al variance \-jere also calculated 
from reductions in sums of squares from fitting of least squares 
constants. 



RESULTS AND DISCUSSION 



Calvinq Interval 



Results presented in Table 2 show the number of calvings and 
mean calving interval observed in the three herds studied. As 
indicated in Table 2, the mean calving interval in Herd 2 was shorter 
(419-3^ days) than that observed in Herds 1 and 3 (432.^8 and -^35.62 
days), respectively. Observed calving intervals in this study were 
longer than those found in studies carried out in temperate countries 
(12, 70, 1)6, 142) but were shorter than those found in European 
dairy breeds under tropical conditions (51, 52, 74, 159). How-ever, 
calving intervals found in this study were not too far from the 
optimum limit accepted by various authors of 14 months. 

Table 3 shows the least-squares analysis of variance for calving 
interval. Year effects on calving interval were highly significant 
(P <0.01) for the three herds. Tables 33 to 38 in the appendix 
present means and least-squares coefficients by years obtained for 
repi-oduct i on data. 

The effect of month upon calving interval was not significant 
for any of the herds studied, Thn^p results were not in agreement 
with the highly significant effect of mionth on calving interval 
reported by Poston et al/ (I52) and Andersen (12) from temperate 
countries, and with those found by Sharda et a|. (I72) for Haryana 
cattle in india. 

The effect of ago of the cow on calving interval was not sfgnifi- 

67 



■ 11^ «Mni muimmv'iii- 



68 



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69 



Table 3. Least-squares analysis of variance for calving interval. 







He 


rd 1 




Herd 2 




Herd 3 


Source of 
















variation 


d.f. 




M.S. 


d.f. 


M.S. 


d.f. 


M.S. 


Total 


^50 






140 




170 




Year 


11 




28,725"" 


11 


21,456 


11 


44,079"* 


Month 


11 




k,%8 


11 


5,907 


11 


8,707 


Sire 


63 




6,410 


17 


5,127 


12 


16,861 


Cow age L, 


1 




1,535 


1 


980 


1 


6 


Cow age Q.. 


1 




258 


1 


121 


1 


541 


Error 


363 




7,024 


99 


6,967 


134 


11,059 



'P <.01 



ii^war^aa^iMnimiiiiitt iMB*i 



70 

cant for any of the herds. These results disagree with those ob- 
tained by Alim (6) and by Sharda at a], (17?-) in their studies with 
Kenana and Hariana cattle, respect i vely. 

intra-herd heritability estimates for calving intervals as 
reported in Table k, were -0.05, -0,15, and -!-0.17, respect i vely , for 
Herds 1, 2, and 3, In the case of Herds 1 and 2, the negative heri- 
tability estimates found can doubtless be attributed to sampling 
error so the heritability of calving interval is considered from 
these data to be 0. Pooled heritability estimate , the overall 
average for the three herds together , were found to be 0,02, These 
results agree with values found by investigators in temperate 
countries (12, 70, 116, 1^2) and with values based on dam-daughter 
correlation reported by Singh and Prasad (176), However, results in 
the present study disagree with some studies (8, 101, 113) of native 
breeds in tropical areas. 

Table 2 shows the number of calvings and the mean intervals for 
the period between calving date and first heat. These intervals were 
different for the three herds. in general, results disagree with 
those intervals reported by some authors in temperate countries. In 
fact, in these studies the range for the interval between calving 
date to first hsat for norma' '-'-■'•■•; ...nc- qq a^%,<- ^.e i-^l-^^l-^-<=^ Sw p..,-!-, 
et a], (/43) and 59 "^ 39 days observed by Chapman and Casida (5^), 
Intervals longer than 60 days as those observed In this study have 
been fouiid by Chapman and Casida (5'0, in reproductive abnormal cows; 
in four times milked and nurse cows as reported by Clapp (56); and in 
first calf heifers and more than seven years old as indicated by Herman 
and Edmonson (89), 



71 



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11 

However, the results are more in agreement with the interval 
obtained by Hirt {3k) of 83.,5 days from Spotted Mountain cattle in 
Germany and with those reported from tropical areas by Dessouky and 
Rakka (66) of 85,52 days in Holstein cattle in Egypt, and 87 days 
observed by Mies Filho and Costa Aroeira (136) in Gir dairy cattle 
from Brazi 1 . 

Table 5 shows the least-squares analysis of variance for calving 
date to first heat. Year effects on the interval of calving to first 
heat were highly significant (P <0.0l) for Herds 1 and 3, and signif- 
icant (P <0.05) for Herd 2. 

The effect of month was not significant in any of the herds, 
in most of the literature reviewed, the effect of month was not 
analyzed; however, Carman (^1-8) found that days to first estrus varied 
markedly from month to month. The highest number of days to first 
estrus was for those calving in March, the minimum in September. In 
some studies, it was found that season of calving had a significant 
effect upon the interval between calving date and first heat. Shorter 
intervals for cows calving during summer were observed by Buch et al. 
{hh) , while shorter ones were reported by Dessouky and Rakha (66) 
from cows calving in spring, 

-,.-.^... ,.„,^, ,iuL :^ i yiii I ; ^,a;ii. ;0r rierUS I ;i\^^ 3, b Li L WG le 

significant (P<0,05) in 'Mr6, 2, 

Ihe ehfect of age of cow was not significant. These results were 
not in agreement with those reported by Herman and Edmonson (89) who 
indicated that first calf heifers had shorter intervals than cows up 
to 7 years old. Age of cow also influenced the interval from parturi- 
tion to involution of the uterus, being shorter in heifers than in 
adult cows, as found by Buch ct al. ('43), 



mrraf . TVTWi ^^ w rta ,o ■ ■ i tffli l MM i Mf 1 I. W l i ml. iMii« » ii i i' i MfiHit.M 



73 



Table 5. Least-squares analysis of variance for calving date to 
first heat. 







Herd 1 




Herd 2 


He 


rd 3 


Source of 














variation 


d.f. 


M.S. 


d.f. 


M.S. 


d.f. 


M.S. 


Total 


450 




1 40 




170 




Year 


11 


5,730"" 


11 


2,959* 


11 


6,056'"^' 


Month 


11 


1,397 


n 


1,615 


11 


2,026 


Si re 


63 


3,579 


17 


3 , 1 29* 


12 


2,349 


Cow age L, 


I 


504 


1 


799 


1 


427 


Cow age Q., 


1 


16 


1 


935 


1 


3,494 


Error 


363 


2,477 


99 


1,797 


134 


2,508 


"P <.05 














"■^•p <.01 















Ih 



Intra-herd he -] tab! li t i es for caivinq date to first heat as 



IndicBted in labls H Ma\-\e(!. 



oni -,27 to Q.33 with a pooled estimate 
of 0,10, The positive values observed in Hards 1 and 2 are not in 
agreement with the reported values found by Hirt (9^-) and Carman 
('48), However, they are quite similar to the heritability vaiues of 
0.27 and 0.32 observed by Olds and Seath {\hS) who indicated that 
the interval from calving to first heat seems to be inherited. The 
negative value observed for heritability in Herd 3 Is probably due 
to sampling error. The true value is probably near 0, 



First Heat to First Service 



The number of calvlngs and the mean intervals for the period 
between first heat and first service are presented in Table 2, These 
intervals varied in a range from 6.35 days, observed in Herd 3, to 
28.56 days found in Herd 2. An interval of 17.64 days was obtained 
in Herd 2. These are lower than that reported by Chapman and Casida 
(5^) of 50 days. 

Table 6 shows the least-squares analysis of variance for first 
heat to first service. The effect of year was highly significant 
(P'^O.Ol) for Herd 1 only. No significant effects of year were 
detected in Herds 2 and 3. The effect of month was not significant 
for Herds 1 and 3, but significant (P<0.05) in Herd 2. 

No significant effects due to sire on first heat to first service 
were observed in Herds 1 and 2; however, a highly significant effect 
(P^O.Ol) of sire was found in Herd 3. 

The effect of age of the cow was highly significant (P<O.Oi) 
for Herd 1 but not in the other two herds. 

Intra-herd her i tabi li ties for first heat to first service were 



75 



Table 6, Least-squares analysis of variance for first heat to 
f i rst service. 







Herd 1 


f 


ierd 2 


Herd 


3 


Source of 
Variation 


d.f. 


M.S. 


d.f. 


M.S. 


d.f. 


M.S. 


Total 


k5Q 




140 




170 




Year 


11 


■ 2,429"" 


n 


1,706 


1] 


273 


Month 


11 


1,537 


11 


1,890* 


11 


335 


Si re 


63 


993 


17 


877 


12 1 


, 1 04" 


Cow age L. 


I 


12,637"" 


1 


386 


1 


127 


Cow age Q,. 


I 


12,966"" 


\ 


410 


1 


110 


Error 


363 


1,184 


99 


1,091 


13^ 


600 


" P < 05 














"" P < 01 















«. -m 8 g7T 1» . SJa».i | i nf , i.»» « . r«r< iiii |a . T|i . 



76 
calculated, and the results are presented in Table h. Negative 
values of -OJO and -0,11 were found for Herds 1 and 2. On the 
other hand, a positive value of -^-0,26 was found in Herd 3, The 
estimated value for the pooled heritabiiity overall average for the 
three herds together was -0.02. 

Mo reported information concerned with the interval from first 
heat to first service was available, so that a comparison with the 
results of this study could be made. 

First heat to first service would not be expected to be heritable 
since the interval is almost completely determined by management 
policies. The variable was included mostly for the sake of completely 
describing calving interval. 

£ljisi,„ Sjir vjc e _^o __Cojnj:j2^^ n 

Table 2 presents means and standard errors for the interval 
first service to conception. Intervals of approximately 60 days were 
observed in Herds 1 and 2, and 97.5 days in Herd 3. intervals obtained 
in this study viere longer than those reported in studies carried out 
in temperate countries which ranged from 28 days as found by Carman 
(48) to 52 days by Pou et al. (153). InPormation was not available 
from tropical countries. 

Year effects on the interval from first service to conception, 
as presented in Table 7, v;5 re hlqhiv s i en" p: --- ■■ 'o < '^'^ f-- ^-u^ 
three herds. These results were not in agreement with those of Carman 
{h8); he found little effect of year on the number of days to con- 
ception. Sire and age of the cow did not show significant effects 
with exception of age linear in Herd 3. On the contrary, highly 
significant differences due to sire effects were reported by Tabler 



77 



Table 7. Least-squares analysis of variance for first service to 
concepti on. 







He 


rd 1 




Herd 2 




Herd 3 


Source of 
















Variation 


d.f. 




M.S. 


d.f. 


M.S. 


d.f. 


M.S. 


Total 


772 






263 




355 




Year 


11 




39,215'"' 


11 


23,42/+"" 


11 


155,811"* 


Si re 


83 




10,598 


23 


9,440 


24 


26,951 


Cow age L, 


1 




6,856 


1 


3,802 


1 


89,136" 


Cow age Q_, 


1 




n,50'4 


1 


1,278 


1 


42,000 ' 


Error 


676 




10,035 


227 


7,262 


318 


20,505 ■ 


" P < . 05 
















'^'^P<.01 

















I » ica >M <r» >..i»j' t a^ c; i 7i » rt »ip i f »ifa»tn Bm »ii^m\m m a^e^st» mm:^ hi#'i i u ^N«i< iL^> w M^m raiifcJiiit;F«w«aww 



78 
et a], (186) in a study of Ayrshire cows. Small effects of age of 
the cow on number of days to conception were also found by Carman 
('18). 

Wi thi n-herd her i tabi 1 i ties for first service to conception were 
found to be 0.02, 0.11, and 0,09, respectively. The pooled heri ta- 
bi lity value was O.O8, Table h shows a summary of her i tabi 1 i ties 
and standard errors for the variable studied. The pooled heri tabi lity 
value of 0,08 is comparable to the 0,07 estimated by Pou et al, (153), 
Smaller heri tabi lity estimates for the same interval were reported 
by Carman (kS) and Dunbar and Henderson (7O). 

Services per ConceptJ on 

Since number of services per conception does not follow a normal 
distribution, two analyses viere carried out. The first was based on 
the actual services per conception whereas in the second a transfor- 
mation of the dependent variable was carried out. The type of this 
transformation was indicated on Materials and Methods In the section 
corresponding to Statistical Procedures for reproduction data. 

Table 2 shows means and standard errors. The numbers of services 
per conception for the original data were 2.0, 2,0, and 2.2, respec- 
tively; the value for the transformed data and for all three herds was 
1,7. These results. In general, are closely in agreement with those 
ioun^ ;n temperate countries in which the values of services per con- 
ception ranged from 1,68 as reported by Boyd et al. (39) to 2.07 found 
by Tanabe and Salisbury (I87). 

On the other hand, results obtained In this study are different 
than those observed In studies with European cattle performing in 
tropical areas, such as the values of 3.3 and 2.3 reported by Joubert 



-■*f^f,tm0> m *iti^f »g« fT a rg;fl |i ^fcfeJM*>B W "'>'l'i w^c u» '»wt*»^ 



79 

(105) from study with Holsiein heifers in South Africa, or the 3,84 

services per conception for Holstein cows in Brazil indicated by 
Carmo and Batista (^9) and the observed services per conception of 
k.6 and S.k for Holstein and Brown Swiss cows, respectively, found 
by Rubio and Salazar (166) in an experimental station located at the 
Atlantic coast of Colombia, 

Tables 8 and 9 show the least-squares analysis of variance for 
services per conception, original and transformed data. Years had a 
highly significant effect (P<.Ol) in the three herds with exception 
of Herd 2 in which the effect was significant (P<,05) when trans- 
formed data were considered. No significant effect of sire and age 
of the cow was observed in Herds 1 and 2, However, sire showed 
significance (P <.05) in Herd 3 and age of cow was highly signif- 
icant (P<,01} in the same herd. 

Within-herd heritability estimates for services per conception 
are presented in Table k. The values for Herds 1, 2, and 3 for the 
original data were, respectively, 0,02, -0.02, and 0,19, For the 
transformed data the values were 0,04, 0, and 0,17, With exception 
of the heritability values observed in Herd 3 of 0,19 and 0,17 for 
original and transformed data, respectively, the other results are in 
agreement with near to zero he ri tabi 1 i t i es found by Legates (116), 
Carman (48), and other investigators, such as Singh (173) who 
reported a heritability value of -0.048 in study with Tharparkar cows 
in India, The pooled heri tabi li ties for the three herds together were 
found to be Q.OB for original and transformed data. 

The low heritability estimates obtained for the variables calving 
date to first heat, first heat to first service, first service to 



80 



Table 8. Least-squares analysis of variance for services per 
conception (original data). 





He 


rd 


I 


He 


rd 2 


He 


rd 3 


Source of 














Variation 


d,f. 




M.S. 


d.f. 


M.S. 


d.f. 


M.S. 


Total 


769 






263 




355 




Year 


II 




1 1. 9"^' 


1} 


k.k- 


11 


26.7- 


Sire 


83 




2.2 


23 


1.8 


2k 


if. 5" 


Cow age L. 


I 




2.3 


1 





I 


28.6*" 


Cow age Q_. 


I 




O.I 


1 


0.2 


1 


20,0 


Error 


673 




2.1 


227 


1.9 


318 


2.7 


" P < . 05 
















"'" P <.01 

















t» M i ■ JM l p ■ .«aA.we'l», T |W ■ * i j r r 1 1 WW *W i I ■ ntB - rT lia i l 'MJl I lM I MfML*. ] l pi | ^rf«MJia 



Table 9. Least-squares analysis of variance for services per 
conception (transformed data). 





He 


rd 1 


Herd 


2 


He 


-d 3 


Source of 














Variation 


d.f. 


M.S. 


d.f. 


M.S. 


d.f. 


M.S. 


Total 


769 




263 




355 




Year 


11 


0.7"" 


11 


0.3^^ 


11 


].l^- 


Si re 


83 


0.1 


23 


0.1 


2k 


0.2 


Cow age L. 


1 


0.1 


1 





1 


l.V^^ 


Cow age Q., 


1 





1 





1 


1.0" 


Error 


673 


0.1 


227 


0.1 


318 


0,2 


" P < . 05 















P <.01 



82 

conception and services per concept i on ,wh i ch are believed to influence 
the service period and consequently the calving interval indicate 
that genetic selection used as a tool for shortening these intervals 
will not or will affect very little the length of the calving interval 
which is a measure of reproductive efficiency. It seerns that the 
lengths of the variables studied are more determined by management 
policies rather than genetic influences. Consequently, improved 
management systems must be emphasized in order to obtain an optimal 
calving interval. This fact is of particular Importance in the 
improvement of dairy cattle in tropical areas. One of the common ■ 
reasons for longer calving intervals, which is typical In many 
European dairy cattle herds in tropical countries, is the relatively 
low level of management to which many of these herds are subjected. 
The lengths of calving intervals observed under the conditions 
of this study could be explained on basis of the gradual improved 
management that has been applied to these herds through the years. 

Gestation Leji q t1i 

Table 2 indicates means and standard errors for gestation length. 
The gestation periods were quite similar for the three herds, being 
280, 279, and 281 days, respectively. These findings were in essential 
agreement with results from Holstein cattle studied in temperate 

countries which has b="=" ^.i-.c«,-,,or-j ^-^^ ,,^^,, ^^„„, o-7r c i-, 

.^,.^^„, ,^^ ^.^ ,^,_ ^ 11,^111 i-iij,sj c^ays as reported 

by Foote et al. (82) to 231.9 days as indicated by During (7I). 
Similar gestation periods of Holstein cows under tropi-cal conditions ' 
have been found, and they ranged from 276 days as indicated by Veiga 
et al. (1S8) in Brazil to 282.6 days found by Ward and Castle (202) in 
New Zealand. 



^> * ^ 'fflHHI^^Kq»^if^^' '"■.-- ' ^-i*ivhi*MKi»MAiHtfB«AM»tllteff1 



83 
Least-squares analyses of variance for gestation length are 
presented in Table 10. No significant effects of year were observed. 
Unfortunately little information in the literature was found on the 
effect of year on gestation length. Most results reported refer to 
the effect of season and/or month of year and these results are 
rather conf 1 icting. 

However, sire affected significantly (P<.05) and highlv 
significantly (P <.0l) the gestation length in each herd. These 
findings are in accord with results of studies with dairy cows in 
temperate countries as well as those from tropical areas. In fact, 
Knott (109) stated the possibility of paternal influence on gestation 
length, and Alexander (5) indicated the conclusive effect of sire on 
the same interval. Significant effects of s i re ,on gestation periods 
have been also observed with native breeds in tropical areas. How- 
ever, Briquet and Abreu (42) from analysis of data of milking Zebu 
cows from Brazil reported that length of the gestation period was not 
influenced significantly by sire. 

No influence of age of dam on gestation length was observed. 
These findings are similar to the results of some investigations from 
temperate countries, such as those reported by Copeland (59), and 
Davis et al. (60). The same conclusion was indicated by investigators 
of native breeds In tropical regions such as Briquet and Abreu (42), 
Singh et al. (I77) and Joubert and Bonsma (IO6). 

On the other hand, many investigators such as Knott (109), Brake! 
et al. (40), Herman et al. (9I). and Stailcup et al. (I8I) have indicated 
that the age of the dam affects the length of the gestation period and 
that adult cows carry the calves for a longer period than younger ones. 



~ ^j -I J CT ■ ■ ii ffTT i >i 1 1 III I ^ f i TffaaT^J Jrr < r ■a e>«_nn Miaw»Bg»^wa>iaic**w 



84 



Table 10, Least-squares analysis of variance for gestation length, 





Her 


d 1 


____Kej-d 


2 


Herd 


3 


Source of 










Variation 


d.f. 


M.S. 


d.f. 


M.S. 


d.f. 


M.S. 


Total 


695 




2i+l 




328 




Year 


n 


3k 


11 


5h 


11 


29 


Si re 


83 


kl 


23 


77"" 


2k 


57^^ 


Cow age L, 


I 


30 


1 


1 


1 


21 


Cow age Q.. 


1 


kh 


1 


10 


1 


5h 


Error 


599 


36 


205 


'-^0 


291 


27 


" P < , 05 














"" P< .01 















-~ 'H i \ *m\ M^ m r .im iiP Tt i-i gr iww^ 



85 

!n most of the reported studies oP gestation length mature cows 
exceeded that oF young cows by about !,5 days. 

In Table '4 are presented the nonmaternal estimates of herita- 
bility for gestation length. The values found for Herds 1, 2 and 3 
were 0.]h, O.36, and 0.33, respectively. The pooled heritability 
estimate for the three herds was 0,28, The values observed in Kards 
2 and 3 were similar to results reported in the literature, in which 
most fall within the range of 0,30 to 0,50, The 0,14 value found 
in Herd 1 is comparable to the 0,10 estimate of heritability reported 
by Everett and Magee (78), 

Fbe m'ean birth weights (mean for both sexes) for the three herds 
are presented in Table 2, Values of 37,8, 36.2, and 38. kg were 
observed. The values obtained are lower than average birth weights 
for Hols-Letns in temperate countries which vary from 40.0 to k3.5 kg 
as summarized by Andersen and Plum (13). 

Table 11 presents the results of the least-squares analysis of 
variance for birth weight. Highly significant effects (P<.01) of 
year were observed in Herds 1 and 3, while no significant effect was 
detected in Herd 2. Studies of Tyler et al, (ig2) and Martin (132) 
confirm this result because they did not find any significant dif- 
ferences between years in t'leir studies with Holbieins In Wisconsin 
and Iowa, respectively. 

Month of year was found to have highly significant effects 
(P<,01) on birth weight of calves on ilci'd 1, This result agrees 
with those obtained by Juma and Kassir (107) from a study with Holstein 
cattle and by Bhalla et al, (30) from Sahiwal data. However, several 



86 



Table 11, Least-squares analysis of variance for birth weight. 





He 


"d 1 


I 


erd 2 


He 


rd I 


Source of 














Variation 


d.f. 


M.S. 


d.f. 
221 


M.S. 


d.f. 


M.S. 


Total 


548 






261 




Year 


8 


41- 


8 


18 


8 


67'"' 


Month 


11 


4r^ 


11 


29 


11 


33 


Sex 


1 


407"" 


1 


17 


1 


385^^^^ 


Si re 


36 


24^ 


24 


28 


23 


27" 


Gest, length L. 


1 


36 


1 


1 08" 


I 


4 


Gest, length Q.. 


1 


42 


1 


119^^ 


1 


1 


Cow age 1.. 


1 


231"" 


1 


669 " 


1 


260 " 


Cow age Q. 


1 


202"" 


1 


536"" 


1 


239- 


Error 


488 


16 


173 


18 


214 


17 


" P < . 05 














"'''' P <,0I 















87 

investigators such as Asker and Ragab (20), Anantakr i shnam and Lazarus 
(10), Tyler et al. (192) and Martin (132) have indicated that month 
of calving and/or season of the year have little or no effect on 
birth weight of the calves. 

Sex of calves showed a highly significant (P<.01) effect on 
birth weight of calves in Herds 1 and 3, These results are in agree- 
ment with the reported I'esults of various authors indicating that, in 
genera] male calves are heavier at birth than female calves. These 
differences seem to be of importance within the Hoi stein breed in 
which the range in birth weights as reported by Andersen and Plum 
(13) goes from hi. 2 to ^5-9 kg for males and from 38.9 to 42,7 kg 
for females. On the other hand, it was found that in Herd 2 the 
weight of the calves was not significantly affected by sex. These 
findings are in accord with the same results observed by Juma and ' 
Kassir (IO7) on a study with pure and crossbred Holstein calves in 
India. 

A significant effect of sire (P<.C5) was found in Herds 1 and 
3, and no effect was observed in Herd 2, However, the value in this 
herd was very close to being significant at the 5% level. An influ- 
ence of sire on birth weight has been reported also by several 
investigators among them Fitch et a], (81), Fcote et al, (82), and 
Roy and Goswami ( 165) , 

Most investigators analyzing dairy data have observed that there 
is a positive correlation between birth weight and length of gestation. 
These positive correlations ranged between 0.25 to 0,52. However, 
in this study gestation length had no significant effect on birth 
weight in 'Herds I and 3. This is in agreement with some few studies' 



that indicated that the correlation between birth weight and gesta- 
tion length is very small or docs not exist. Among these studies 
are those reported by Eckles (72), McCandlish (13'i-) and Fitch et al. 
(81), Hovjever, it is important to mention that the above three 
investigations were based on a rather small number of animals which 
is also true of this study. 

Age of the cow, linear and quadratic, had a significant effect 
(P<,01) on birth weight. These results are in accord with findings 
of most authors that have studied birtli weights of dairy breeds in 
tropical as well as temperate zones. 

Table '4 pi'esents the wi thin-herd and pooled nonmaternal herita- 
bility estimates for birth we'ight. Values of 0.1-^, 0,26, 0.2'+, and 
0.22 were found for Herds 1, 2, and 3 and the pooled value for the 
three herds, respectively. These values are lower than those reported 
by the few investigators that have studied the heritability of birth 
weight of dairy cattle, in fact, heritability estimates varying 
from 0,38 to 0.60 have been reported by Legault and Touchberry (118), 
Blackmore et ai, (3I), Tyler et al, (19?-), Askar and Ragab (20), and 
Roman et al . (164) . 

Reasons for _Djs |303 aj_ 

A total of 352 cows was utilized to determine reasons for ■ 
t. , o,j.^_..j , , , ij^p, w^M 11,^ ^.^ , y' ^j,a vv^-iG sold and 15% died. 

A summary of wi thin-herd reasons for disposal with their respec- 
tive percentages is presented in Table 12, The main reason for disposal 
in the present study was low reproduction at kk, kG , and 35% for Herds 
1, 2 and 3, respectively. The pooled value for the three herds was " 
found to be 41%. These values are higher than those reported in the 



89 



Table 12, Summary of i-easons for disposal. 





Herd 


1 


He rd 


2 


He rd 


3 


Reasons 


Mo. Cows 


% 


No. Cows 


% 


No, Cows 


7o 


Sold 


167 


87 


h\ 


73 


91 


88 


Low Reproduction 


8k 


hh 


26 


46 


36 


35 


Low Production 


11 


37 


\h 


25 


32 


31 


Age 


6 


3 






10 


10 


Mi seel laneous 


h 


2 






8 


8 


Accident 


1 


1 






5 


5 


Mast! tis 


1 


1 


I 


2 






Died 


26 


13 


15 


27 


12 


12 


Diseases (Misc.) 


12 


6 


1 


2 






Aborti on 


5 


3 


1 


2 


5 


5 


Bloat 


2 








5 


5 


Accidents 


2 




2 


4 






Masti ti s 


1 




1 


2 






Dystocia 


1 




1 


2 


1 


1 


Hemopai"as i tes 


1 




8 


14 






Pneumonia 


1 








1 


1 


Acetonemia 






1 








Unknown 


1 


1 




2 






Total 


193 


100 


56 


100 


103 


100 



i'i' " ir"«wrww>*yr»'n m Tt J W* t ^ 



90 
literature which ranged from 7% as reported by Seath (17!) to 33% 
as tound by Salazar (I67), However, it is important to mention that 
the principal reason for disposal reported by most authors included 
in the review of literature was low production and not low breeding 
efficiency. The pooled value of k]7o found in this study was in 
agreement with the estimate obtained by Parker at a 1 , {]h7) who 
reported h]7o of disposals due to low reproduction. High percentages 
for low reproduction found in the present study might be partially 
explained by the sources of the data studied. Special care of 
reproductive abnormalities has been given to the cows of these 
experimental herds and the cows are culled soon after breeding 
difficulties are present. On the contrary, most studies mentioned 
above, and as was pointed out by Parker et al. ( Uf7) , were based on 
the data from DHIA herds. They, for example, often would consider as 
a low producer a cow which has been open for a prolonged period, 
which really should have been identified as a difficult breeder. 

Low production was the second major reason for disposal and the 
pooled percentage for the three herds together was found to be 3k. 
The observed values for Herds I, 2, and 3 were 37, 25, and 31%, 
respectively. These values are compared to those reported by several 
authors ranging from 16% as reported by Evans et al, (77) to 3^i% found 
by Asdell (I6), The higher value of 37% observed in Herd 2 could be 
explained because the size of this herd allows the culling of more low 
producers while maintaining satisfactory milk yield and adequate 
numbers of replacement heifers. in Herd 3 the percentage of cows 
culled for low production is less than in Herd I mainly because this ' 
herd is much smaller and nearly all the cows in this herd must be 



"«»=n?wfl>«r»-i"MMWBi<»^» 



) 



c 



91 

retained to maintain adequate milk supply and production of replace- 
ment females. The low percentage of cows culled in Herd 2 is 
partially explained also by the small size of this herd and mainly 
by the relatively high death loss (27%) which limits the number of 

:ows available to be culled for low production. It is important to 
notice that the category of cows culled for dairy purpose is not 
included in this study as is reported in most of the studies reported 
in the literature on reasons for disposal. This could be explained 
because the relatively small size of the herds studied does not permit 
culling cows for dairy purposes exclusively. In most of the cases 
the cov/s culled for low production in the three herds studies were 
used as dairy cows by those that purchased the cattle. The level of 
production of the covis culled may not be satisfactory for the minimum 

ilk production required in the experimental herds, but provide 

nough production for the standards of the commercial milk producers. 
For the purpose of summary, other causes for disposal such as 

ge, miscellaneous, accident, and mastitis were classified in one 
category which accounted for 10% of the disposals. The value observed 
in Herd 1 was 6% while in Herd 3 the percentage was 22, No information 
was available for age, miscellaneous and accident in Herd 2, Conse- 
quently, the value of 2% corresponded only to mastitis. The higher 
percentage found in Herd 3 for this group of causes as compared to 
the relatively lovj value observed in Herd 2 could be explained on the 
higher percentages for cows culled for age (10%), miscellaneous (8%), 
and accident (5%) in contrast with the values of 3%, 2%, and 1% found 
for the same respective causes in Herd 2. 

As was mentioned before, approximately 15% of the cows died for 



m 



e 



a 



-"— °- ~^-'^ 



92 

different causes. The death losses in Herds 1 and 3 were quite similar 
being 13% and 12%, respectively. However, a much higher percentage 
(27%) of cows died in Herd 2. A possible explanation of this finding 
could be that the true tropical conditions existing in Station 2 with 
more adverse climatic effects, have affected more drastically the group 
of cows in Herd 2, Under these conditions a high incidence of diseases 
and parasites is present. Table 12 shows the high percentage (li|%) of 
death due to hemoparas i tes , contributing to the overall higii death 
losses in this herd. Death due to hemoparas i tes such as anaplasma, 
babesia, and piroplasma is common in cattle under tropical conditions 
and occurs mainly in European cattle subjected to this type of environ- 
ment. 

Main causes of death in Herd I were miscellaneous diseases and 
abortion which accounted for 6% and 3%, respectively. in Herd 2 the 
higher percentages corresponded to hemoparasi tes and accidents with 
]k% and k%, respectively. The major causes of death in Herd 3 were 
abortion and bloat with a combined value of 5%. 

Because the information on reasons for disposal and mainly those 
reasons causing mortality are not uniform from one study to another, 
it is difficult to make a comparison among the different studies on 
the topic. 

In general, the results in the present study suggest the emphasis 
that have been paid in the three herds to reproductive problems. This 
is reflected in the high percentage of culling found for low reproduc- 
tion. 

Sex Ratio and Twinning Rate 

From 1,365 calvings studied in the three herds a sex ratio of 



93 

53% for males, 4?% for females, and ] .kn for multiple births was 
obtained. Table 13 shows the sex ratio and twinning rate in the 
three herds studied. 

The sex ratio observed in this study is in agreement with that 
found in several studies and summarized by Johansson (99), 

The values for twinning rate are lower than the percentage of 
3.3 for the Hoi stein breed reported by Johansson (99), and compared 
to the value of 1,8% indicated by Asker and El-!triby (I7). 

The small number of calvings on which the present study was based 
compared with the large volume of data from which Johansson (99) 
made his report could account for the discrepancy of the results. 

.Production 

In Table \h are presented the number of records, means, and 
standard errors for milk, fat, and k% FCM yields from first calf 
heifers, mature cows and all cows. 

Average milk and fat yields for all cows ranged from 3,ii63 and 
\2k kg to i^,506 and I53 kg, respectively. These yields were in the 
range observed in experimental Holstein herds in tropical regions. 
However, average production of Herd t surpassed the higher production 
of 3,900 kg reported by Hirsch and Schindler (93) in Israel. These 
results were also comparable with findings of Roman et al. (I63) 
at high altitudes of Ecuador. Fat yield averages were lower than 
those reported for Holstein cattle in temperate countries. However, 
they were comparable with reported values found in tropical areas. 

It was observed that production in Herd. 1 exceeded that of Herds 
2 and 3 by 1,000 and 8OO l<g , respectively. Since climatic conditions 
in Herds 1 and 3 were similar, differences in production could partial 1 



y 



Jtn«ikc»c II m w t ^ tf j i;t* l » 7 iWi^ M P ffa i*aBMaC»illtti 



table 13. Sex ratio and twinning rate. 



3k 





He rd 


1 


He rd 


2 


Herd 


3 




Number 


% 


Number 


% . 


Number 


% 


Sex 














Ma 1 e s 


37^^ 


53 


1^0 


52 


195 


5h 


Females 


338 


'47 


129 


^8 


169 


46 


Total 


712 


100 


269 


100 


3Sh 


100 


Bi rth Type 














Si ngles 


712 


99 


269 


97 


36 '4 


99 


Twi ns 


9 


1 


7 


3 


h 


\ 


Total 


721 


100 


276 


100 


368 


100 



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o 



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a. 



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96 

be explained by the different genetic backgrounds of the original 
populations. Herd 1 was founded with imported registered Holstein 
cows from Holland, Herd 3 was formed originally with groups of pure 
and grade Colombian Holsteins, The same was true for Herd 2. However, 
for this herd, climatic conditions were quite different from those 
prevailing in Herds 1 and 3, 

Table 15 shows the number of records, means, and standard errors 
for the Independent variables affecting production data. Tables 39 
to k7 in the Appendix present mean yields and least-squares coefficients 
for years and months. 

It is noticed that in Tables ]k and 15 the number of records 
analyzed in the all cows group is not the sum of the other two groups. 
Since in the analyses of mature cows the variable previous dry period 
was considered, only records with this information were included in 
this group of cows. However, when all cows were studied previous 
dry period was not included in the model. Consequently some records 
not considered in analyses of mature cows were included in the all 
cows group, increasing the number of total records. 

Year and Month o f Caivin_g 

Tables 16 to 2k show effects of year and month on dependent vari- 
ables studied. In general, year of freshening affected production 
significantly (P<,01) in Herds 1 and 3. However, In Herd 2 this 
significance was only detected in the group of all cows. 

Least squares analyses showed no significant effect of month of 
calving upon yield in Herd 3, On the other hand, significant effects 
(P<.01) were found in the other two herds. Conflicting results have 
also been reported by other investigators in tropical areas. Variation 



97 



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99 



Table 17. Least-squares analysis of variance for fat yield for first 
calf heifers. 







■lerd 1 




Herd 2 




Herd 3 


Source of 














Vari ation 


d.f. 


M.S„ 


d.f. 


M.S. 


d.f. 


M.S. 


Total 


1^7 




99 




60 




Si re 


36 


1 , 239''" 


18 


ii-68 


10 


287 


Year 


3 


3,91 T"' 


5 


hS 


8 


184 


Montli 


11 


587 


11 


695 


10 


253 


Age 














Linear 




9^7 




1,863"" 




l,2ii5 


{Quadratic 




28 




22 




595 


Length of record 














Li near 




12,99^"' 




2,182"" 




4,050"" 


(Quadratic 




3,^175"" 




2ii0 




378 


Days open 














Li near 




226 









76 


Quadratic 




2,708 




51 




43 


Residual 


91 


5^+8 


59 


361 


26 


609 



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!02 

Table 20, Least-squares analysis of variance for fat yield for mature 
cows. 







Herd 1 


..■^^ — 


Herd 2 


He 


rd 3 


Source of 










vari at ion 


d.f. 


M.S. 


d,f. 


M.S. 


d.f. 


M,S, 


Total 


303 




172 




145 




Si re 


53 


1,621""' 


18 


2,491 


15 


369 


Year 


10 


if, 320"" 


12 


1,572 


9 


1,883*" 


Month 


11 


492 


11 


2,131 


11 


446 


Age 














Li near 




2,lif9*" 




171 




1,721"" 


(Quadratic 




5,707"" 




60 




2,460"* 


Cubi c 




1,312 




1,762 




2,355"" 


Length of record 














Li near 




24,128"" 




36,747"" 




6,703** 


(Quadratic 




25 




8,494"" 




164 


Days open 














Li near 




68 




I9,36r"' 




153 


Quadratic 




80 




48,080'"^ 




369 


Previous dry period 














Linear 




3,462"" 




2,651 




6 


(Quadratic 




3,816"" 




2,855 




1 


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220 


702 


122 


1,955 


101 


535 


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'■— vO l^~ 


en LA 


VO ■-:i- -d- 


CO r^ 


cn en CM 


o »s 


« f\ ^ 


CO CO 


vo -^ — 


CO LA 


CO r^ r^ 


~ r\ 


— ^ ^ 


ev », 


«» 


vO '- 


,— 


CO 





CO LA »— 
- vo — 
-ci- 



o 

-4- 















•a 
























L. 
























o 
























(J 




















U 




QJ 




u 






o 


































+J 








-I-' 






+J 








U 


fO 




<■!- 


u 


ra 


c 


1_ 


CO 








03 


I.. 


o 


o 


<0 


!_ 


0) 


fO 


!-, — 








11) 


"O 


o 




(D 


-a 


D. 


CD 


■u tu 








c: 


(U 


-Q 


sz 


C 


fa 


O 


c 


fO 3 


--— 


-C 




.— 


3 


ZS 


■i-> 


• — 


3 






3 "O 


iTl CJ L. 


^-l 




._! 


cy 


CJ 


CD 


_J 


Ci' 


1/) 


-J 


o-.r: 


J-J U (TJ 


c: 


OJ 








C 






>. 




iji 


O — (l) 


O 


DO 








OJ 






ra 




CD 


— OO >- 


e: 


< 








_J 






Q 




a: 



o 

V 



Table 23, Least-squares analysis of variance for Fat yield for al 
cows. 







Herd 1 




Herd 2 




Herd 3 


Source of 














variation 


d.f. 


M.S. 


d.f. 


M.S. 


d.f. 


M.S. 


Total 


498 




283 




218 




Si re 


65 


1,553"" 


27 


1,695 


18 


664 


Year 


11 


12,5^3"" 


12 


],k8k 


9 


2,773"" 


Month 


11 


1,267'"' 


11 


1,312 


11 


491 


Age 














LI near 




3, '456"" 




310 




7,888"* 


Q^uad ratio 




17^530"* 




9,217"^' 




18,750"" 


Cubl c 




47 




100 




17, 261'"^" 


Length of record 














Li near 




V4,523"" 




38,594"" 




12,239"" 


(Quadratic 




2,549"" 




10.263'"' 




434 


Days Open 














Linear 




k7 




15,476"" 




5 


(Quadratic 




186 




39,191'"'' 




228 


Residual 


hok 


733 


226 


1,370 


173 


476 



P<.01 



->* ■ ? <■ *.4t a*H «rir« tf -[V.tr^;w raM^^ I'^rcWCf* r > i <>«i j it j. -««k»<5^ 



!06 



u 

m 

u 
O 



■D 

(U 

■M 

u 
m 
t- 

o 
o 



m 



o 

o 

c 
ro 



to 

> 



(/I 



i/i 

OJ 

u 

(0 

I! 

cr 
I 

■M 
10 

(H 

0) 

-J 






fl3 



■X) 



XI 



Lr\ ca uA 
u-\ r-^co 
Lr\ r-^ CM 

o-i CO o 
CO ra csl 

-J- l-O CM 



CO CO (T\' 
CM 



C^l CM -d" 

ao r-- CM 
c^ r^ i_A 

i-Pi — O'^ 
O — LA 

o r--. r-- 
un — o 



O CO 

og J- 
o cvj 
-d" m 
00 



CA CM o 

r— vo — 
uTv CM r--- 

— vX) 

LA CA 

CM 



rA 



LA <N J- 


r-- ua — 


o>co 


c■^ o 


CM 


CA \iD CM 


a> CTi o 


~ o 


J- oa 


r-v 


-d" r-- LA 


— o r-- 


LA rv-i 


o^co 


<T\ 



X> 



~o 






M- C 

o o 

0) +-> 

(J ro 

3 L. 

o lu 

00 > 



cor--i^ r-.MDcA [\(^ voooot 

CM^O LAO OLPv lACvlUA 

r--LAvO u"^o OLA oo-J- 



vO 



-Ci" LA 

CM 



J- 00 



OA r^ CM 
00 CM r— 
CM 



VO 
CM 
CM 



: 5c :;; 


J- 


4< 5: 






-- vO CA 


O^vO o 


00 ir\ 


OA 


— o 


J- r^co 


O^ lA O 


.- C-J 


Csl 


LAOD 


o r-- — 


CM 0"^ ■— 


CA LA 


CO 


CA CM 


^ »* ^^ 


»S (N ^ 


A n 


.-s 


rt *. 


J- V.0 CM 


CO VO CM 


cnvo 


-1- 


— VO 


r-- o o 


LA rA — 


,— LA 


o 




o^co 00 


LA CA 


O VO 




-4- 



CO 



CO LA ' 
CTiVO ' 



o 



o 
o 

0) 



-l-J 



ro 
O 



OJ O 



fO !.- (J O fU 

0) T3 — OJ 

c fo -in jr c 

.— 33+-' — 

-J O' CJ) OJ -J 

<IJ c 

DJ CU 



iX! 



TJ 



C U (X) 

OJ (0 u 

Q- OJ XJ 

flj O C CO 

rj, .- D 

cy CO -_i cy 

10 il) 



"O 



O 



V 



"^'*'«^'T^ "»rF" "Wr« ^ ' g « 7» ' il '< f'^ ^ V I^I^I1»*»'t'm<S»g » il i t t r - j i,— ~.i»it»n«»l|F.r 



107 

in yield vji th month of calving was not significant In several 
studies (39, 111, 121, 125, 170, 175, 199), On the other hand, 
significant differences have bsai reported by other investigators 
(32, 57, 1^1). The fact that month effects differ should not be 
surprising since climate varies among the different areas. Measuring 
the effects certainly has value in every study to help describe and 
characterize the data and to avoid making poor estimates of other 
effects due to disproportionate distributions of records oyer months. 

Mean age at first calving was 33 months in Herds 1 and 2, and 
32 months in Herd 3. These means are in agreement with those obtained 
in temperate countries which vary from 27 to 3'4 months, and comparable 
to those reported for Holsteins under tropical conditions. 

Peak production was attained by the group of mature cows in 
which average age varied from 65 to 70 m.onths. It has been reported 
that European dairy breeds reach maximum production around the fifth 
lactation. However, results found In this study are closely In 
agreement with those reported from European breeds under tropical 
conditions which in most cases attained maximum yield before the fifth 
lactation. 

Results revealed that increasesin milk, fat, and k7o FCM up to the 
miaximum mature age varied rrom 12% to 30%, ThiCse figures can be 
considered to be similar to those obtained in Hoi stein cattle under 
temperate and tropical conditions, in which I ncreases var ied from 19 
to 32%. 

Tables 16 to 2'f show that effects of age at first calving on 
yield were not significant in tlerds 1 and 3 but highly significant 



i08 
(P<,01) in Herd 2, On the other hand, age significantly influenced 
yields of mature cov^s and combined groups. In general these results 
agree vji th most studies in temperate as v;ell as tropical areas. 

Due to lack of available information on age correction factors 
from the tropics, in general, and particularly from Latin American 
countries, it was of interest to include a preliminary analysis of 
data with respect to this topic. 

Age correction factors were estimated with the objective of 
gaining knowledge on differences between correction factors calcu- 
lated in temperate countries as compared with those obtained under 
tropical conditions, it is important to emphasize that if differences 
in correction factors between cattle of temperate and tropical countries 
exist, it would be incorrect to use conversion factors for age obtained 
in temperate zones. Consequently, correction factors should be based 
on data fi'om the area to which they are applied. 

It is recognized that, because of the small number of records 
included in this study, the accuracy of results is not optimum. How- 
ever, this preliminary information could give some idea of the magni- 
tude of real differences. 

Based on approximately 1,000 records, age correction factors 
were calculated separately for each herd by using m.ethods indicated 
in statistical procedures. 

Table 48 of the Appendix shows the age correction factors derived 
in this study. In general the factors obtained are quite similar to 
those found for Holstein cows under temperate conditions. Since the 
factors obtained in this study differ little from those reported for 
temperate countries, it is suggested that the latter continue to be 



■ -rT-ltr >T f^' "" t "ifl * W'ffl ^'' ^ ' — TT*''-'T M "t' t » ff T* J » 



109 
used in Colombia until more realistic figures based on a larger volume 

of data can be generated, 

_Lenqth of Recor d 

Average lactation lengths for records truncated at 305 days 
varied from 292 to 299 days. These figures are in agreement with 
averages observed in Holstein cattle In temperate areas. Since 
records longer than 305 days were not considered, however, it was 
not possible to compare these results with these obtained from 
Holstein cattle in tropical countries which have been shown to vary 
from 29^t days as found by Boyazoglu (37) in South Africa to 370 days 
as reported by El-!triby and Asker (73) in Egypt, 

Only about 1% of the lactations ended before 200 days. This 
figure is lov.'er than the 5% observed among European dairy cattle in 
temperate countries, and with 5% reported by Mahadevan (125) in his 
study of European dairy breeds in Ceylon. By contrast, 21% ended 
before 300 days. This value i s ' comparable to findings reported from 
tropical areas in which lactation show a great variation in length. 
Mahadevan (126) indicated that among unimproved Zebu breeds as many 
as 25% may end before 200 days and even among improved Zebus 60% have 
sometimes been recorded as ending before 300 days. Pearson et al. 
(148) found that variation in lactation length for BON' and BON-Jersey 
crossbreds in Colombia accounted for 9^% of the variance in yield. 

Tables 16 to 2k indicate that length of record significantly 
affected all measures of production in first calf heifers, mature 
coww, and ail cows. These results were in agreement with those 
observed in cattle under tropical conditions where a high correlation 
between yield and lactation length has been found to vary from 0.'+ as 



"■"■T'---'> "'^' ii TiT ^(•^--^^'"■f r-i ■ ' f fc r'^'-T- Tr~ 'Tihr^l r' 



110 

reported by Mahadevan (126) to 0,9 according to Naidu and Desai (I38). 
Verde (199) showed that linear and quadratic effects of length of 
record on milk yield v\'ere sta t i s t i cal 1 y significant in pure and cross- 
bred Holstein cattle in Venezuela, 

Days Open 

Table 15 shows that mean values for days open in first calf 
heifers, mature, and all cows varied from 15^ to 2]k days. !n general, 
tiiese means were larger than most of those reported In the literature 
(22, 102, 178). Particularly, long periods were observed in Herd 3 
in which they ranged from 192 to 2]k days. 

Records vjith more than 300 days open accounted for 12% or more 
in each herd. Percentages of 12, 18 and 21 were observed in Herds 
1, 2 and 3, respectively, Approximately 7% of the records in the 
three herds had less than 60 days open. 

Results of analyses (Tables 16 to 2h) showed that, in general, 
days open did not significantly affect the dependent variables 
studied. These results were not In accord with findings of several 
uthors (76, 158, 178, 180) in which days open significantly in- 
fluenced production. On the other hand, contradictory results were 
found in Herd 2 where linear and quadratic effects of days open on 
fat and 4% FCM of mature and all cows were detected. These findings 
were in agreement with the significant effect of days open on fat 
yield of Jersey cows in Florida reported by Barrantes (22). 

The contradictory effects of days open observed in this study 
suggest a need for further investigation of this factor in dairy 
cattle records in tropical countries. 



a 



1 1 1 

Table 15 shows means and standard errors for previous dry 
periods which varied from 87 to 116 days. Even though these figures 
were not similar to the optimum length dry period of 60 days suggested 
by several authors in temperate studies, they were in the range re- 
ported for European cattle under tropical conditions which has varied 
from 9^ days as reported by EI--itriby and Asker (73) to I'+l days as 
found by Verde (I99) in Venezuela. 

Least-squares analyses of data from Herds 2 and 3 (Tables 19 
to 21) sliowed no significant effect of previous dry period on yields. 
These results were in agreement with several studies conducted in 
temperate as well as in tropica] countries which have indicated that 
number of days prior to calving did not greatly influence lactation 
yields unless the dry period is quite short. On the other hand, 
linear and quadratic effects of previous dry period were statistically 
significant in Herd 1. A possible explanation of this result is the 
greater number of records with previous dry period of less than kO 
days observed in Herd 1 as compared with the other two herds. Approx- 
imately Z87o of the records in Herd 1 were in this category while 9 
and 21% were observed in Herds 2 and 3, respectively. 

Her itabi 1 i ty • 

iauie 25 Si'iows wi tl'ii n--hierd and pooled liei'l tabi I i ty esLimaLes froiii 
paternal half-sib correlations calculated from the least-squares 
analyses. Formulas used in these calculations are indicated in 
statistical p|-ocedures. Standard errors were estimated by the formula 
reported by Swiger et a], ( I S'l-) for unequal subclass numbers. 

Heri !:abi 1 i ty estimates on a \;i thi iv-hsrd basis for First calf 



i ^.^-f^vu^fna^ttmiti^sMiiM^ ■Tr-- | : i .'j : w I ' r nm - ■ j "i-ii^im'"iiwli«>T-<s»ai 3l »'< M tf -B 



12 



o 

u 

4- 



U 

o 

c 
o 



(J 

■o 
o 

s_ 

Q. 

O 

^' 

01 



J3 




to 




•M 




•Ma 




1_ 




« 




jr 




T3 




m 




|-V> 




O 




O 




Q. 




T} 




C 




(13 






• 


"O 


C/l 


L 


ci; 


0) 


U1 


_c 


>- 


1 


I—— 


c 


m 


c^ 


c 


_c 


ra 


■4-J 




.» 


!/) 


? 


(0 




L. 


q- 


m 


O 


rj 




cr 


>- 


C/) 


I. 


1 


rO 


-4 -J 


1-- 


10 


b 


10 


3 


(1) 


00 




« 




LA 




CM 




0) 








J3 




(0 




h- 





0) 
O 

o 



-o 






(U 

3: 






o 
1>J 


o 

(N 


Csl 


M3 


OJ 


~-i- 


rA 


ro 


— 


o 


O 


O 


• 

O 


o 


o 


O 


O 


o 


- 1 


-h 1 


•-1- 1 


+ 1 


-1- I 


+ I 


+ i 


-i- 1 


+ 1 


O 


O 


1.A 
O 


o 


O 


• 

o 


rA 

vO 

» 

O 


O 


5- 

» 

o 



VO 


VO 


oo 


VO 
CM 


(^ 


OO 




VO 


CM 


O 


O 


o 


O 


o 


o 


o 


o 


O 


+ 1 


+ I 


-!• 1 


-1- 1 


+ 1 


+ I 


,t_ 1 


+ 1 


-!- 1 


CM 


0"\ 


o 


LA 
CM 


LA 


LA 

o 


o 

VO 


CA 


rA 


O 

1 


o 

1 


o 

1 


• 

o 


• 

O 

1 


• 

o 

1 


o 


O 


O 



CM 


CA 


CA 


o 


O 


O 


f i 


-!- i 


+ 1 


o 


CM 


rA 


• 

o 


• 
O 


O 



o 



CO 

CM 


o 

Csl 


CM 


o 


o 


O 


J. ( 


-i- 1 


-r I 


C-J 

-4- 


CM 


VO 

Cvi 



o 



o 


O 


o 


1" I 


+ 1 


+ 1 


VO 
CM 


o 


CM 



o 



VO 


VO 
CA 


VO 

CA 


LA 
Csl 


CA 
CM 


csl 


CA 


VO 


r-v 


o 


O 


O 


O 


O 


O 


o 


o 


• 
o 


f 1 


+ 1 


-1- 1 


-]' i 


-V 1 


-!- 1 


-h I 


-l~ I 


-i- 1 


CM 

> 


VO 


vD 

(V\ 

• 


O 


VO 


l-A 
00 


vO 

OO 


CA 

LA 


CM 
VO 

* 



o 



o 



in 


















v_ 


















<U 


















"4- 


















(D X> 






T3 






"O 






_c — 


-o 




f— 


X! 






X> 




(U 


■ — 




(/I CD 


. — 




CD 






M- — 


CD 




> • — 


CU 






<u 




— >- 


.™ 


5_ 


O >~ 




st 


>- 




?" 


ro 


>- 


O 


CJ 


>- 


CJ 


m 


^ 


(_) 


u ^i. 




U^ 


^ 




u. 


3 -^ 




1,1. 


' — 


-l-i 




0) — 


■i-1 




O — 


-i-j 




■\-j »— 


(U 


sf 


u .._ 


fO 


s^ 


u — 


CtJ 


'^ 


01 i. 


U- 


■J- 


D s: 


Li- 


^- 


s: 


U. 


-t 



U- 



wiwf.-->i«(r» t0%:, ■ .rwr^r^n-aw^gnjBiBi 



113 

heifers, mature cov;s and comiDined ccv/s, all shov^/ed a vjide range in 
values. Including all her i tab i 1 i ties for milk, fat, and 4% FCM 
yields, the estimates varied from -0,05 to 1,36, Pooled herita- 
bilities varied from 0,2'+ to 0,71. 

In general, herltability values found in this study vjere some- 
what higher than most reported estimates in temperate as v,ie]l as 
tropical countries. The high values found were in agreement with 
0,76 estimated by Gur" Yanva (88) In Russia, 0,60 indicated by 
Johansson and Rendel (100) in Denmark, 0.55 reported by Naufel ( UM ) 
in Brazil, and 0,71 found by Magfoke and Bodisco (121) in Venezuela, 

A second estimation of herltability was carried out by using the 
components of variance obtained from nested analyses based on adjusted 
records of all cows. The adjustment was based on information pre- 
viously obtained from the least-squares analyses. In Table 2S are 
presented results of these analyses for Herds 1, 2, and 3. Table 
27 shows a summary of wi thin-herd and pooled herltability estimates 
by paternal half-sib correlation calculated from nested analyses. 
In calculating standard errors of heri tabi 1 i ties , the modified formula 
of Dickerson (68) was used. Herltability estimated from this set of 
data ranged from 0.09 to 0.82. Pooled herltability estimates were 
0.65, 0.31. 0.52 for milk, fat and i;% FCM yields, respectively. 
Particularly high values of O.8O were observed for milk yield in 
Herds 1 and 3. 

To explain the wide variation In estimates from different herds 
and age groups and particularly the high pooled herltability estimates 
observed in this study several hypotheses can be formulated. The 
herltability estimates computed from first calf heifer and mature cow 



wk 



fable 26, Analysis of variance for production data of all cows 
adjusted for all significant effects except for sire, 



Source of 
variation 



d.f. 



Milk yield 
M.S. 



Fa t yield 
M.S. 



'!-7o FCM 
M.S. 



Total 


^99 


Among si res 


65 


Among cov-vs wi thi n 




si re 


117 


Among records in 




cow in s 1 re 


317 



Total 

Among si res 

Among cows wi thi n 
si re 

Aimong records in 
cow in s i re 



Total 

Among s i res 

Among cows v/i thi n 
si re 

Among records in 
cow in s i re 



283 
27 

86 
170 

218 
18 



Herd 1 

1 , 7'48 , 756 "" 2 , 083" " 1 , 1 80 , 6 1 r' 

563,^^7"^ 
325,85^ 



661,213"" 1,512" 



359,0ii-6 706 

He£d_2 

69^,165"" 2,567 



Vr* 



i^56,8lV 



953 



218,35^ 1,339 

Herd 3 



1,013,838' 



65 358,738' 



135 132,581 



797 



if73' 



382 



987,271' 
388,675 
^M'f,853 



-Wf 



62i^,59I"' 
283,895'"' 
166,683 



"" P< ,01 



15 



Table 27. Summary of wi thi n~herd and pooled her i tabi li ties for 
production records of all cows estimated from nested 
analyses. 



Variable Herd ] Herd 2 Herd 3 Pooled 

Milk yield 0.82;^ 0,28 0.23 :!;0. 2^4 0.80 ;!: 0.43 0.65:!:0.l8 

Fat yield 0.09 1 0,21 0.51 t 0.20 0.25 t 0.21 0.31 t 0.12 

k% FCM 0.54 t 0.25 0,53 t 0.23 0.48 t 0.30 0,52 t 0.15 



a»J&«^)iif**»*74 



o 



116 

records separately vary widely between herds and eilso batv/een age 
groups. A part of this can be explained on the basis op inadequate 
subgroup numbers. The standard errors of the estimates viere generally 
high and considerable inconsistency was not surprising. indications 

f a more disturbing inadequacy of the data arise from results obtained 
by pooling the two age groups, all cows, in Herd 3, The generally 
negative estimates for separate age groups turned strongly positive 
for all cows combined (Table 25). A possible explanation could be 
that pooling of data resulted in inflation of sire variances due to 
time trends. 

Estimates for all cows in both Table 25 and 27 look unreal is- 
tically high even after discounting them somewhat in view of sizable 
standard errors. The discrepancy between these estimates and 
repeatability estimates shown in Table 28 likewise suggests that sire 
variances reflected effects other than the breeding value of sires, 
or that genetic differences between cows for some reason were much 
less than differences between the sires included. 

Considering all possibilities it appears that the factors most 
likely to have contributed to the apparently inflated sire variances 
were: 1) non--rcmovabl e envi ronmiental correlations resulting from 
time trends rnay have resulted in non-adjustable confounding of sire 
and environmental effects; 2) assortative mating in which the choice 
of sires to which dams were mated was not entirely a matter of chance; 
or 3) unusually distinct differences in genotypes due to the wide 
range in origin (U,S,A, , Holland, Colombia) of sires represented. 

Estimates of repeatability of lactation records bv intra-class 



117 



Table 28, Summary of wi thi n-herd and pooled repeatab i 1 i 1: i es estimated 
from production records of all cows. 



Variable Herd I Herd 2 Herd 3 Pooled 



Milk yield 0.27 t 0,06 0,32 t 0.07 O.k) t 0.08 0.31 t 0,04 
Fat yield 0.33 t 0,06 -O.!^ t 0.05 0.09 t 0.09 O.OB t 0.04 
4% FCiM 0.24 '^ 0.06 "0.03 t 0.07 0.22 ! 0.09 0.13 ;!; 0,04 



'-»•^t-•lsffl»«r.7i»s^^^cmIS'-^s*«^•»is»;■^^T«■«»^"»«*^lF 



118 

correlations of adjusted records of all cows are presented in Table 
28, !l shovis a summary of wi thin-herd and pooled repeatabi 1 i t ies 
calculated by using formulas indicated in statistical procedures, 

V/i thi ii~herd repeatability values for lactation yields showed 
the same wide variation that was observed in heritability estimates 
already mentioned. Values ranging from --0,03 to 0,'i-l were observed. 
Pooled values were 0,31, 0.08, and 0.13 for milk, fat, and k7o FCM 
yields, respectively. The unusually low value for fat and k% FCM 
yields as compared with that for milk yield is surprising in view of 
the part-whole relationship between the different measures of produc- 
tion. Repeatabi 1 i ti es obtained from these data in general are among 
the lowest of those given in the literature from temperate countries 
which average approximately 0,50. Mowever, repeatabi 1 i ties for milk 
yield were within the range of those reported from European cattle {]k, 35, 
121, 1^1, 179) in tropical areas which vary from 0.31 to 0,65. 

The small number of records included in this study and the year 
to year variation in climate and management could be reasons to 
partially explain the contradictory results observed. 

i'^l.'.'.^^-J'.Y. S i. rQ in tg r a c t i on 

Data analyzed for this part of study consisted of i■^56 records 
from "203 daughters of 20 different sires from iJ„S,A„, Holland, and 
Colombia used by both Ai and nalufal service. Data included were the 
adjusted responses based on least-squares coefficients estimated in 
analysis of data from all cows, in this study were considered only 
sires with daughters in 2 or n'ore herds, and those daunhters with 1 
or n-or-e records. Thiese data are summarized by herds in Table 29. 



Table 29, Summary of herd x sire data 









Herds 






1 




2 


3 


Sires 


20 




15 


12 ' 


Daughters 


91 




63 


49 ' 


Av. daughter per sire 


k. 


6 


k.2 


'4.0 


No. of records 


210 




137 


1 09 


Ave, records/daughter 


2. 


3 


2.2 


2,2 


Leasts-squares means 










Mi Ik yield (kg) 


^,220 




3,713 


3,648 


Fat yield (kg) 


158 




117 


131 


4% FCM (kg) 


3,884 




3 , 2/42 


3,411 



120 

Values for components of variance associated with herd, sire, 
herd by sire effects and differences among paternal half sisters 
(residual) are given in Table 30. Corresponding percentages which 
each component comprises of the total variance are also presented. 
Tables kS to 51 in the. Appendix shovj rank of sires by herds for mill<, 
fat, and h% FCM yields. 

The sire by herd component of variance surpasses in the case 
of fat and k% FCM yields the magnitude of the sire variance. For 
milk yield sire component was found to be greater than herd by sire 
component. Herd, sire, and herd by sire affected significantly 
(P <.01} milk, fat, and i'r% FCM yields with exception of sires on fat 
yield In which no significant effect was detected. 

The fraction of total variance for milk, fat, and 4% FCM yields 
due to herds ranged betvseen 8 and 19%, variance due to sires between 
to 13%) 3nd remainder variance between 70 and 75%. In general, 
these figures agree with results obtained in several studies {kS , 117, 
201), However, the fraction of total variance due to herd by sire 
interaction ranged between 5 to 10%, These results were in disagree- 
ment with most studies (45, 117, 133, 201) in which the fraction of 
total variance due to herd by sire interaction was zero or near to 
ze ro , 

Sire by herd interaction effects have not been of major importance 
in most studies previously reported. The general conclusion derived 
from these investigations vjas that ranking of a group of bulls, based 
on their daughter's performance in a given herd, would be expected to 
be substantially the same when the bulls are compared on basis of 
daughters performance jn other herds. True ranking of bulls was 



121 



Table 30, Least-squares analyses of variance components and per- 
cent of total variance. 



Source 



Total 

Herd 

Si re 

Herd x s i re 

Remai nder 



Total 

Herd 

Si re 

Herd x si re 

Remai nder 



d.f. 



M.S. 



Components 





Milk yield 




h55 






2 


7,800,948"'' 


48,726 


19 


1,256,278V? 


41,910 


25 


685.013"" 


37,789 


i^09 


319,594 
Fat yield 


319,594 


455 






2 


36,697"" 


240 


19 


1 , 1 29 , 


8 


25 


1 ,605'-""' 


69 


409 


941 


941 



% of^jota 



11 


8 


9 


13 


8 


9 


71 


70 



19 


14 





4 


5 


9 


75 


74 



1,°/ pTM 



Total 


455 


^'-^1- 








Herd 


2 


9,572,720';" 


60,161 


13 


10 


Sire 


19 


702,294'-"' 


16,523 


4 


7 


Herd x sire 


25 


7 86, 7 79 '"~"' 


46,927 


10 


10 


Remai nder 


409 


332,991 


332,991 


73 


72 



Calculated from components of variance 



Calculated from reductions in sums of squares from fitting of 
least squares constants 



122 

apparently the same even though they were In herds with different 
production levels (I33, 161), under different management systems 
(130, 133), and if daughters of bulls have been artificially or non- 
artificially bred (201). Finally a broader regional aspect of such 
interactions has been recently considered (120) and evidence indicated 
also that a bull may be safely selected and used for Ai In one region 
even though he was evaluated In other region. 

The highiy significant herd by sire interactions found In these 
data could be explained in two ways: 1) the Interaction is real, or 
that 2) the data were inadequate due to small volume of records or 
confounding of sire effects with time trends which were incompletely 
removed. 

If It is assumed that the d'lfferences were real, failure to agree 
with other reports could possibly be explained on the basis of: 1) a 
wide range In genotypes of sires tested In this study, a view supported 
by a widely divergent origin of sires; 2) environmental differences 
between herd locations were large. This suggestion Is supported by 
variations in production levels in the three herds, due to nutritional 
and managerial conditions, and by obvious climatic differences between 
the locations of the herds. 

The possibility of genuine limitations existing In these data 
has been indicated. The magnitude of the Interactions observed, how- 
ever must be interpreted as being suggestive of a real interaction. 
The widely accepted use of semen from temperate countries to 
Inseminate dairy cattle In tropical areas emphasizes the importance 
of gaining knowledge about the contribution of genotype by environ- 
mental interactions. It is suggested that some attention to these 



''g(iwwii«r*iwi M ' :> « " '»'* . i" ^>j | ? "^t W ' ». ii » - 



23 



interactions must be paid in future animal breeding research in 
tropical areas, in general, and ,speci f i cal !y , in Latin American 
countries. 



SUMMARY ANO CONCLUSIONS 

Genetic and envi roninv".nta1 factors affecting reproductive and 
productive performance of three experimental Hoi stein herds v;ere 
studied. Herds viere located at three different regions of Colombia. 
The data analyzed covered the period from 1956 to 1967- Some 1,390 
gestations and 1,002 lactations v;ere considered in the analyses. 
Data were analyzed separately for each herd by using least squares 
as the major , analyti cal technique, 

I _ 4- u _ - .. _ 1 , _ £ ,_ „ .J . . ^ <- ; , . ^ - -, u-.i- ,-, .i: r .-, _ J- ^ ^ c ..oat- r-~.-> "i 1- U 

III i.iiv-'. f.i 1 iu ! y jv" o ui i i.;p I i./t.' i,j.^ u 1 vi.; ii;i.»jiu.j si i ici., lj Oi ycdij niOnLn, 

sire, and age op cow upon calving interval, calving date to first 
heat, first heat to first service, first service to conception, 
services per conception, gestation length and birth weight v;ere 
studied. 

Overall means for calving interval varied from klS to k^S days. 
These intervals were close to the opti-nal limit of ]h months reported 
in studies from temperate countries. For the sake of describing 
calving interval, several factors affectijig the service period were 
included in this study. The overall intervals observed for Herds I, 
2, and 3, respec t i ve ly ,were : for caivinc date to first heat, 86, 63, 
and 93 days; for first heat to first service 18, 29, and 6 days; for 
first service to conception 61, 60, and 98 da-/)-. The average number 
of services per conception was 2,0 for the t'lree herds. 

The effect of year on ti'.e variables studied was hiighly significant 
in ail the cases except for thie interval first iicat to first service 

1 2k 






125 

in Herds 2 and 3 where no significant effect was detected. Usually 

sire and age of darrt did not have a significant effect on the variables 

studied. Paternal half-sib pooled herltability estimates ra-<aed from 

-0.02 for the interval fis-st heat to first service to 0,!0 for calving 

date to f i rst heat. 

Overall means for gestation period ranged from 279 to 281 days. i 

No significant effects of year or age of cow were observed. However, \ 

significant effects of ssre in the three herds were detected. The i 

f 
pooled heritability Vv-as 0>28. 

Variation in calving interval as a measure of reproductive ! 

efficiency is mainly influenced by environmental factors rather than 

by genetic causes. This is confirmed by the heritability estimates 

found for the two factors Influencing calving interval, Lov,' herita- 

bilities were observed in the variables included in service period, 

whereas moderate estimates were found for gestation length. These 

findings suggest the importance of im.provsd menagerjal practices to 

I 
maintain a high reprod;jcti ve efficiency in Holstein cattle subjected I 

to the conditions of the three different environments included in 

I 

this study. j 

Mean birth weights for both sexes varied from .36 to 38 kg. These 

values were lower than avB-Bae birth weights for Holsteins in temperate 1 

1- 
countries which vary from kD to ^4 kg. Highly significant differences j 

due to sex 'were observed in Herds ! and 3. Mean values for females ! 

were 37 and 36 kg , respect lye ly, A value of 39 kg was found for males ' 

in both herds. No significant effect of sex was found in Herd 2 and | 

the mean values for /nales and females were 37 and 36 kg, respectively. 

In rfios: c£jses there were significant effects of year, age of dam and 



126 
sire, !n genera!, months and gestation length did not affect birth 
weight of calves, Within-herd pooled heritabiltty estinates ranged 
from 0. ]k to 0,26, 

Major reasons for cow disposal were low reproduction which 
accounted for k]7o of disposals in the three herds. Low production 
and a group of causes such as age, miscellaneous, accident, and 
mastitis were also principal causes for culling with 3k and 10% of 
disposals,, respectively. Approximately 15% of the cows died for 
different causes with Herd 2 having the highest death loss. The 
emphasis that has been paid in the three herds to reproductive problems 
Is reflected in the high percentage of culling found for low reproduc- 
tion. 

From 1,365 cslvings studied- a sex ratio of 53% for males, and 
47% for females, and ] A7'% for multiple births, was obtained. 

Effects of age, length of record, days open, previous dry period, 
year and month of calving, and sire upon milk yield, fat yield, and 
k%- FCM were studied on milk production data. 

First calf heifers had means for age, length of record, and 
days open of 33 months, 298, and 173 days, respectively. Average 
milk yield, fat yield, and 4% FCM ranged between 2,910 and 3,872; 103 
and 134; and 2,693 and 3,558 kg, respectively. Mature cows averaged 
68 months, 296, 175, and 98 days, for age, length of record, days 
open, and previous dry period, respectively. Average milk yield for 
this group of cows varied from 3,685 to 4,885 kg, 

in general, analyses indicated that age significantly affected 
yields of mature and all cows. Effects of age on first calf heifers 
were not great. Increases in yields to maturity varied from 12 to 30%, 



1 27 

Lactation length s i gni f i cot i ve ! y affected production in all tliree 
groups of cov/s studied. 

Days open did not affect s i gni f icat! yely milk production. How- 
ever, contradictory results were found for fat and h7o FCM yields. 
It was not possible to detect a significant effect of previous dry 
period on production performance of Herds 2 and 3. - On the other hand, 
linear and quadratic effects were statistically significant in Herd 1. 
A higher percentage of records in Herd 1 with dry periods of less 
than ^-i-O days could explain these results. 

Wide variations within and between-herds vjere observed for 
heritability and repeatability estimates. Pooled heritability values 
were 0.65, 0.31 and 0.52, respectively ^for milk, fat, and k% FCM 
yields. For the same dependent variables, pooled repeatabi 1 i ties 
were 0,31, 0,08 and 0.13, respectively. Limitation in number of 
records, non- removable envi ronmisntal correlations, assortative mating, 
and unusual differences in genotypes of sires represented were con- 
sidered as possible factors contributing to the wide variation and 
high heritability estimates observed, A small volume of data and 
year to year variations in climatic and management, could be reasons 
to pai'tially explain the contradictory results found for repeat- 
abilities. 

Some h5S records from 203 daughters of 20 different U„ S. , 
Ho! land, and Colombian sires were onalyzed to estimate herd by sire 
interactions. Herd by sire components of variance 5!.;rpn<?sed in most 
cases t!ie magnitude of the sire variances. Herd, sire, and herd by 
sire s ig!ii f i ca ti ve !y affected milk, fat, and k% FC/M yields 'with 
the exception of sires on fat yield in v/iiich no significant effect 



128 

vias detected. The failure to agree with most other studies vihere 
little or no herd by sire interactions have been detected might be 
explained by the vn de range in genotypes of sires tested, a view 
supported by the vjidely divergent origin of sires, or that environ- 
mental differences between herd locations were large. The small 
volume of data Vi,'as also a limiting factor in this study. However, 
the magnitude of the interactions observed suggested that attention 
to these interactions must be paid in future animal breeding research 
in tropical areas. 

Lastly, the performance of Hoi stein cov^s in the three herds 
studied indicated that good repro'iuct i ve efficiency and satisfactory 
levels of production can be achieved if adequate selection and v*ell 
m.anaged programs are provided. These results suggest that Holstelns 
can be used successfully to increase milk yield in the three regions 
represented in this study. 



APPENDIX 



Table 31. Reproduction data card layout. 





Variable 




Columns 




1. 


Station No, 




1 




2. 


Animal No. 




2-6 




3. 


Generation No. 




7 




if. 


Breed Group 




8-9 




5. 


Si re Code No. 




10-12 




6. 


Breed Group 




13-1'+ 




7. 


Dam No. 




15-19 




8. 


Breed Group 




20-21 




9. 


Date of Bi rth 




22-27 




10. 


Gestation No. 




28 




11. 


Date of Last Parturition 


29-34 




12. 


Date of Fi rst 


Heat 


35-40 




13. 


Date of Fi rst 


Servi ce 


41-46 




]h. 


Date of Concep 


tion 


47-52 




15. 


Conception Bull (Code) 


53-55 




16. 


Breed Group Sire 


56-57 




17. 


Services per C 


Dnception 


58 




18, 


Date of Partur 


i tion 


59-64 




19. 


Sex and Defect 


of Calf 


65-66 




20. 


Generation No. 


of Calf 


67 




21. 


Breed Group of 


Calf 


68-69 




22, 


Calf Number 




70-74 




23. 


Bi rth \le\ ght o 


f Calf 


75-76 




2h. 


Pxeproducti ve D 


i sorder 


77-78 




25. 


Cause F.nd of Rt 


2 cord 


79-80 





Table 32. Production data card layout. 



131 



Var I abl e 



Col umns 



1 . Station No, 

2. Animal No, 

3. Generation No, 
k. Breed Group 

5. Si re Code No. 

6. Breed Group 

7. Dam No, 

8. Breed Group 

9. Date of Birth 

10. Lactation No. 

11. Date of Parturition 

12. Age of Parturition (Ms.) 

13. Days Dry Before this Part. 

14. Length of Lactation 

15. Milk Production (kg) 

16. Fat % 

17. Milk Fat Production (kg) 

18. Solids Non Fat .(%) 

19. Persistency 

20. Cause End of Lactation 

21. Conditions Affecting Lactation 

22. Classification of Lactation 

23. Date of Pregnancy during Lact. 
2k. Average Body Weight 

25. Grain Consumption 



1 

2-6 

7 

8-9 
10-12 
13-14 
15-19 
20-21 
22-27 
28 
29-34 

35-37 

38-40 

41-43 

44-48 

49-50 

51-53 

54-56 

57-58 

59-60 

61-62 

63 

64-69 

70-73 

74-77 



132 



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r«M»>UMi,'>My^anMitaC« lai mA — t ^- 



138 



Table 39, Mean yields (kg) of first calf heifers by years within 
herds. 




Herd 1 



Group 



Years included 



I 


1956-60 


h\ 


3,775 


135 


3,531 


2 


1961-62 


37 


4,396 


155 


4,084 


3 


1963-64 


38 


3,221 


112 


2,974 


k 


1965-66 


32 


4,165 


134 


3,678 


Total 


1956-66 


148 


3,872 


134 


3,558 


Herd 2 






. 






] 


1955-57 


18 


3,468 


i]4 


3,098 


2 


1958-59 


11 


3,767 


531 


3,472 


3 


1960-61 


7 


3,985 


139 


3,677 


k 


1962-63 


18 


3,776 


126 


3,396 


5 


1964-65 


24 


3,376 


107 


2,950 


6 


1966-67 


22 


2,832 


96 


2,573 



Total 



1955-67 



00 



3,430 



14 



3,083 



Herd 3 



1 


1959 


2 


i960 


3 


1961 


4 


1962 


5 


1963 


6 


1964 


7 


1965 


8 


1966 


9 


■ 1967 



3 


2,490 


91 


2,366 


6 


2,840 


108 


2,756 


1 


2,891 


98 


2,626 


2 


2,564 


89 


2,307 


12 


3,207 


i08 


2,898 


16 


2,954 


106 


2,771 


12 


3,057 


105 


2,792 


6 


2,986 


102 


2,717 


3 


1,516 


57 


1,456 



Total 



! 959-67 



61 



2,909 



!02 



2,693 



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O^-J" (N-d-vOCO r^CO-4-vO-- 0^l■A 
CM fA^<■^mfAc>-^-j■ fv^voaonrACsl cM 






cn 



— cMiArAcsir^or^-j-mvo — — 
CNlo~\OOMDmcX)vOooi-r\l — ^r^vo 

— vococnr^— i-AOcor^LAoJvo 



CMLAOLAOCMLAi^OlACsIcpiVO 
^- r.- CM CM C-J '— — — ra CM J- J- 



.— r^r.-- r-v.rn^ cTiCO r-^— CO o 
J-cncor^coOLrN'— coco — Csl 
CM oco r\r-~-LnvD-J"vO ror^cN 



m r--, r^- o"i rA I — 'vO r-s. (j^ I — j- c^j 

CM lA CXD i— CO [^ ort. CM (v^ viD !A O^ 



O (N CO 1^1 vX) ~ O i- Q -— O CTi 
C7^J' CT^— CTi-d" COCX) C"~\COcnco 

-j-m— c^jcDcoor--~cri0^oco 



CO J- LA LA LA -d" 



CA CA -T LA LA 



r-- CvJ r-. CO OA i-A -Cj- LA -J' ^O LA O 
CM C^J OJ c<'^ OA -t LA ^O r^ LPi LA '— 



LA vo r-- CO cr^ o — c\i ca J- la vo r^ 

LA LA i-A LA LA VO \0 U":) vO ^O VO 'vO VO 

o^ o^ o^ o^ CA o^ o^ o■^ o■^ ca o^ oa o-> 



(V-\ 



oO(j\csico-a'-cNjr\ovo -:i- 

CO ' — CM vO CM CN CM CM C^l o CM 



LAr-~-4'r^LALACOvX)LAJ' CA 

-J- r~-- -J- CM o -j- vo o J- r^ M3 

OOlAOLAvOC^LA-d'O -^ 



CA 



LAvor--wCNjcMr-~-cr\cr\' — (j\ 

, — , — , — ^-- CM CM J- CA CM ■ — 

CM 



00 
CA 



CO 

Csl 



CA 
OO 
vO 



J- 
00 
Csl 



O 
O 



■^ 



fA 

LA 



VO 
O 
LA 



CA 



O 

1- 



- <f^SI;?w:=iW«SW^S- ' 



tig-L-'j crair»u ^' V 



un 



Table k2. Yearly least-squares coefficients for production data 
of first calf heifers. 



Milk 



Fat 



4% FCM 



Herd 1 



Group 


Years incl 


uded 


1 


1956-60 




2 


1961-62 




3 


I963"6if 




h 


1965-66 




Least-s 


qua res mean 




Herd 2 






1 


1955-57 




2 


1958-59 




3 


I96O-6I 




k 


1962-63 




5 


I96V65 




6 


1966-67 




Least"S 


qua res mean 




Herd 3 






1 


1959 




2 


i960 




3 


1961 




i+ 


1962 




5 


1963 




6 


I96it 




7 


1965 




8 


1966 




9 


1967 





91 


k 


Sk 


271 


13 


300 


742 


-21 


-612 


380 


k 


218 



3,057 



06 



2,816 



271 


- 2 


-]kk 


-k7h 


k 


-132 


-296 


•• 3 


-167 


91 


- I 


17 


655 


.3 


267 


295 


3 


159 


,979 


105 


2,763 



-231 


"13 


-287 


- 22 


1 


8 


1,168 


61 


1,377 


-128 


- 9 


"188 


172 


k 


133 


- 27 


3 


42 


- 67 


-12 


-201 


- 25 


"22 


-432 


- 62 


-14 


-452 



Least-squares mean 



2,481 



98 



2,458 



\k2 



in 

B 



2: 



c<\ (J^ ir\ -^ 00 \0 kO \0 r^ c'-\ vo 

II I I I •> 



CD 

3: 



TO 



f a — r<^ . — . — csi 

II t II.— 



O h^— LA-J-'— O^LACTl-:)" 

r^ >~a -4" — r<-\ LA cN t^ J- -d" 

V.O c-4 (v-^ J- ^- UA CNI ,— csl 

II I III 



00 
-4- 



03 

u 

3 

m 
E 

^- 
O 



o 



VO r^OA(nLACO>sD CM — I^^J- cr\ ,— 

r— LAJ"'~o^^rALr\(Nocri r^ 

LA -4- -C^ CM J- CM j- 

III 11 






rA 



fl3 

c 
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csj 












r-^ 


r-- 


CA 


CA 


t-^-t 


-4* 


-i- 


CSl 


vn 


CM 


fA 


CA 


CM 


1 


, — 


7 








I 




LA 



-J- 



o 

3 

•u 
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t- 
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CTlCACMvO'- LA-Cf r^-4"CM 

^ — C^J -d" O vO CTi — 

.— r— oA CM mD J^ — 

III III 



C^J 


CTl 


CA 


r^ vr\ 


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^ CM 


1 


vO 



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3 ,. 

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u) 

+J' 

TO 



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rA 



J3 



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3: 



3: 

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<i- 



n3 






MDCOOO CM r-~Ci^'— MDCO^oJ" 
00 CPvr^CnLAtT\0 CMOOvOVO 
~cM^_:i-rALAvOr--~ -j- 

I I I I I 



LA 



1- 
to 

CD 



J- O '— rA r--. fA vO (T^ J' -J" — - c^ 

CslcMcM. — cMcMrM . — . — r-> 

I I I I I — 



oa^c->iLACMcOr--cMrAcPvr^ ■-- 
' — — c^)r^r~-.cM — J-LAvocM c-a 
VO -4" rA CM vO u^ r-~ CA fA r~-~ CO 

II III 

10 
to 
u 

m 

3' 
0. 

J/J 
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UA vO I — ^ 00 en O . — CM rv-\ -j- LA "^O r^ i/l c 
LA LA LA LA LA vO vO VO V.O vD vO vD VD CO CO 

G^ o^ o~^ o"^ cn cj^ cj^ o^ CTi CTi o^ o~^ o^ OJ cw 



1^3 



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CMvDl"~~~0^ — CslCMcPlVO 

00 CM .— r-- ,— (v^ cvj _ jNj 
I i I II 



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LP, — 

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Ln-4--c|-00vot-rvCNl 



CM 



Jsi 



(^r^-4'M3'~cNj — LncMLa 

vour\J-ODrocMoor---(>^rsi 

r^cNcN-j-. — -4"— CM 

II I II 



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vo 



10 

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<r\ r<^ -^ en (^ 

<^ . — CM 

I I I I 



LA-^-:tJ"vp LPvCTiOp or>r-^ 



00 o 



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LA 

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0^vOCM--r^CM.— rv. — v£)CMLa 
I I I I ! " I I 



r--— coco o^i^— — vo— \£i-c|-r— 

CMr- CM -d--j- CM — cv-ij- 



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— -d-c^J-d-voj-cMvoJ-CsI,— [^ 



I I I 



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O^oa-:t00v0 — OCOCX) Lr\r»^^D 
(V^ ^- ^-. ,_. CM CM ^- CM — CM 

II I I I I 



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CO oa LA -- CX) J- cv-, vo -:i- ►— O lAi 
CAr^— LALA-^ CMvO LA-J- LAO^ 






00 
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o^cy^c^^o^O'^a^o^c^lO-^o-^o^o~^CT^(iJ cu 



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OOvOro CNI(v^-^'-r-- — O 
— ^ CN CM oa -J- CM 

II I i I 



VD 



vD J" 00 r»^ rv-\ CM J- r^ cpv 

III T I 



LacTAvo <^r — J-00 i\o r^ — 

0OCM00-4-VD-J" i-N r-xCOOLA 
— -:J- — CM — j-~j-„ 
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<N CM J- (X) O 

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■— -:f ctvCN^jo r^cMOcor-^r^co 

00OJ--:t00 CMvD LACACnoO CM 

-rJ-UPvCM ^ CMr— LA^ CM 

I II III 



!_ 

0) 

x: 



CJ 



-t 



4-1 
TO 



ocMvx)cncocsiLar--r-^-j-r^-;t 

tNJ- OOOvO — CA P^O'— 

eg cM„_cMfA -d- — ro 

I III I 



r^uArocr\fACM r^cM-^- o-d--c|- 

— CM ^ 

I I II II I 



CO 
LA 
-4- 



CXD 

cn 



CO 



CN 



cnuf\c^LALr\ — J- — cA— r-.o ca 

u-\r^— OvX)vor--.r'~\cr\i-Ar^LA md 

cofArA'— ' — cm. — LA^ ' — r\ 
I III i II 

CM 



LA -J- r^ fA ~t LPi 

CM — O 

I II — 






CO 



vo 
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coa^ocMj-cocMcn—iAo^— r\ 

o■^c^^^Mo■^Ln — cooco-:^'— vo la 

CM , — (A. — CACM-J-. — ^ , — CM O 

II ill I .^ 



>- U 

1- m 



c 
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c: 



3 -C 

L- U 



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TO 0) TO 



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(u >^ 3 M o 0) 0) 

!- >■- c .— o") CL -I-" > u n3 ra 

D. TO D 3 n oj u o (D 0) aj 



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J-n^iwi^rf-^fSrvifT^T-- 



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r— -j- -j- r-- LA o o^ LA -J- cTi '— r^ 

CTi -:!"'— — vD r-^ r-~- cA i-^-^ r^ o 

r— ^- CSI CNl — 

I I I I I I II 



Csl fv-i <N — -4" CO c^ 
III I I 



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o r^ en r-~. (v^ 

VO csl en CM 



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■ CO -J- CM LA '— LA \o 

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1/1 
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LAr^LALACM^i) r^co I^o^J■ (T\ 

cM-d" — . — cv-^vOLAO — roCNO 

CMCNI CM rvlcMCM — . — 

I I I 



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LA 
LA 
CM 



vOrACMC)OcMrv-\or^CMr^CNlr~^ CO 
111 I I •— 



— OvOOAOr-^r-.OLAOA-4-CM pa 

cMrsicAOA—r^r^i^rAcn cm o 
— CM — CM CM r-^ 

11 111 I -^ 

CA 



c 

0) 



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Ci~\ — MDvoJ'vO-4-— O^— cni-A o 

r~»cO' — (TicTic^JJ"' — ooAP^r-- oo 

^ ^ ^ ^ ^_ — OA — o 

I I 1 I I I I 



a 
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ro 

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— r^ r-~. en LA 
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r~^ — rA rA -J" LA 
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r^cvlv^oA-d"cMcorACM. — r— ,-- 
\0 0-:t--:l- cnoco r-^LAi-AvD-^"- 

■ — CM .— CMi — ■ <— rA CM 

111 III I 



CA 

LA 



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•"5 u- S < :■<:. ~o "o < c/-> o z; Q _i E 



m ' lri^ M Ull " * « V l i F»l' ' li " » 



Tnwj i ir i "»ft i»r^iiin rrja jw 



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C^J — I r— ^— r^ (V-l fW 

I I I I II 



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CM— — CNj — i — c^ o^ ^ 

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14/ 



Table 48. Age--correct i on factors for 305"day production records, 



Herd 1 HejlU- JrliLlJ. Herd 1 

Age Factor Factor Factor 



1-6 


l.it55 


1.365 


1.684 


1-9 


1.403 


1.363 


1.595 


2-'0 


1.357 


1.294 


1.518 


2-3 


1.315 


1.263 


1.451 


2-6 


1 . 278 


1 . 249 


1.393 


2-9 


1 . 2hh 


1.219 


1.342 


3-0 


1.214 


1.183 


1.298 


3-3 


1.187 


1.160 


1,258 


3-6 


1.116 


1 . 1 40 


1,223 


3-9 


1.147 


1.121 


1.191 


it-0 


1.126 


1,104 


1.164 


if- 3 


1.102 


1.089 


1.139 


i|-6 


1.085 


1.074 


1,117 


z,„9 


1.071 


1.061 


1.097 


5-0 


1.068 


1,049 


1.080 


5-3 


1 , 046 


1.039 


1,065 


5-6 


1.036 


1.029 


1.052 


5-9 


1.028 


1.022 


1 . 040 



Age 


Factor 


6-0 


1.020 


6-3 


1,014 


6-6 


1.009 


6-9 


1.005 


7-0 


1.002 


7-3 


1.001 


7-6 


1.000 


7-9 


1.001 


8-0 


1.002 


8-3 


1.004 


8-6 


1.008 


8-9 


1,014 


9-0 


1,020 


9-3 


1.028 


9-6 


1.036 


9-9 


1.047 


10-0 


1.058 


10-3 


1.071 



-■gt^W gi & ffg iWJiagW^aSc ugUi WW tjm-ryr m 



Table kS. Continued 



I '48 



Herd 2 Herd 3 
factor factor 


Age 


Herd 1 
Factor 


Herd 2 
Factor 


Herd 3 
Factor 



1.015 


1.030 


1,010 


1,022 


1.006 


1,015 


1.003 


1,009 


1.001 


1.005 


1.000 


1.002 


1.000 


1.000 


1.002 


1.000 


1.005 


1.001 


1.009 


1.003 


1,010 


1.006 


1.022 


1.010 


1.031 


1.016 


1.029 


1.023 


1.053 


1.031 


1.067 


1.0^0 


I.O83 


1,051 


1.073 


1.06^ 



1.0-6 
10-9 
II-O 
11-3 
11-6 

11-9 
12-0 

12-3 
1 2-6 
12-9 

13-0 
13,-3 

13-6 

13-9 
]k-0 

lit-3 
K-6 

14-9 
15-0 



.086 
.103 
.121 
.]k] 
.]Sk 
.191 
,218 
.2^9 
,283 
.322 
.365 
.413 
.'^67 
.529 
.598 

.677 
,768 

.873 
.996 



1.088 
].]he 

1.139 
1.204 
1.238 
1.278 
1.323 
1.374 

1.^33 
1 .502 
1.582 
1.675 
1.787 
1.921 
2.084 
2.289 
2.551 
2,897 
3.373 



.077 
.093 
.110 
.129 



.]7k 
.200 
,228 
.260 
.294 
.333 
.375 
.422 

.475 
.533 
.599 
.673 
.757 
,852 



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LITERATURE CITED 



1. Abdel-Ghani , W. , and S. K. Fahmy. I966, Productivity of 

Friesian and its crosses in UoA.R. Agric. Res. Rev,, Cairo, 
kk{k):37. 

2. Abelein, R., and H. C. Ritter, 1959- Relationship between birth 

weight and weight at one year in heifer calves in a Spotted 
Mountain herd in Grub. Mitt, bayer, Landesanst, Tierz, Grub, 
7:1^5 (cited in Animal Bdg, Abstr, I96O, 28:1857). 

3. Agricultural commodities - Projections for 1975 and I985. I966. 

Food and Agricultural Organization of the United Nations. 
Vol. 1. 339 pp. 

• k. Ahmed, I. A,, and A. 0, Tantawy, 1956. Causes of variation in 
the gestation period of Egyptian cows and buffaloes. Empire 
J, Exptl . Agri , , 2^:213. 

5. Alexander, M. H. 1950. Length of gestation in the five major 

breeds of dairy cattle, J. Dairy Sci., 33:377- 

6. Alim, K. A. I96O. Reproductive rates and mill< yield of Kenana 

cattle in Sudan, J, Agric. Sci., 55:183, 

7. Amble, V. N., K. S. Krishnan, and P. N. Soni . I963. A review 

.of the breeding results obtained in some Indian herds of 
dairy cattle. Proc. ]kth Meet. Anim. Husb, Wing Bd. Agric. 
Anim. Husb. India, Bangalore, 1961:^28 (cited in Animal Bdg, 
Abstr. 1965, 33:392). 

8. Amble, V. N, , K. S. Krishnan, and P. N. Soni. 1967, Analysis 

of breeding data of some Indian herds of cattle. 1 . C. A, R. 
Tech. Bull, (Anim, Husb.), No. 6. New Delhi: Indian Council 
of Agricultural Research. 37 pp. (cited in Animial Bdg. Abstr. 
1969, 37:216). 

9. Amble, V. N. , K. S, Krishnan, and J, S. Srivastava. 1958. 

Statistical studies on breeding data of Indian herds of dairy 
cattle. I. Red Sindhi herds at Hosur and Bangalore, Indian 
J. Vet, Sci,, 28:33 (cited in Animal Bdg, Abstr, 1959, 28:156. 

10, Anantakri shnan , C, P, , and A. J, Lazarus, 1953- Observations on 
some Indian cattle. Pt, IV, A study of the birth weight of 
calves. Indian J, Dairy Sci., 6:23. 



152 



153 

11. Anantakrishnan, C. P., A. J, Lazarus, and M, C. Rangaswamy, I952, 

Observations on some Indian cattle. Pt. II, Some causes for 
the variation in the length of gestation. Indian J. Dairy 
Sci., 5:63, ^ 

12. Andersen, H. 1966. Effect of season, age and herd size on 

fertility in cattle, Arsberetn. Inst, Steri 1 i tetsforsk. K. 
Vet.-og Landbohojsk. , 1966:227. (cited in Animal Bdq. Abstr 
1967, 35:2ii09). ^ 

13. Andersen, H. , and M. Plum, I965. Gestation length and birth 

weight in cattle and buffaloes: a review, J Dairy Sci 
^48:1224, ^ 

Ul. Arave, C. W. , R. C. Laben, and S, W. Mead. 196^, Measurement 
of genetic change in twelve California dairy herds J 
Dairy Sci. , 47:278, 

15. Arnold, P. T. D. , and R, B. Becker, I935. The effect of season 
of the year and advancing lactation upon milk yield of Jersey 
cows, J, Dai ry Sci . , 18:621 , 



16, 



Asdell, S, A. 1951, Variations in amount of culling in DHIA 
herds. J, Dairy Sci,, 34:529, 



17. Asker,_A. A., and A. A, El-!triby. 1957. Calf losses, sex 

ratio, abortion and twinning of native, European, and cross- 
bred cattle in Egypt, Indian J, Dairy Sci,, 10:191, 

18. Asker, A.^A,, A. A, El-!triby, and S. K. Fahmy, I962. Factors 

affecting initial milk yield in cattle in the United Arab 
Republic. Indian J, Dairy Sci., 15:81, 

19. Asker, A, A,, K. H. Juma, and S, A, Kassir. I966. Dairy 

characters of Friesian, Ayrshire, native, and crossbred 
cattle in Iraq, Ann. Agric, Sci. Univ. A' in Shams,, 10:29. 

Asker, A, A,, and M. T. Ragab. 1953. Causes of variation in 
birth weight of Egyptian cattle and buffaloes. Indian J 
Vet. Sci,, 22:265. 

Bachner, F. I95I, Birth weight of Spotted Mountain calves, 
Tierzuchter, 3:368, (cited in Animal Bdq, Abstr 1951 iq- 
I669). 



20, 



21 



22. Barrantes, R. E, I963. Effects of various environmental factors 

upon milk production of Jersey cows, M. S. thesis. Univer- 
sity of Florida, Gainesville, 

23. Bayley, N. D. , and E. E. Heizer. 1952. Herd data measures of 

effect on certain environmental influences on dairy cattle 
production, J. Dairy Sci., 35:5^0. 



15^ 

2k. Becker, W, A.. I968. Manual of Procedures in Quantitative 

Genetics. Washington State University Press, Washington 
State University, Pullman, Washington. 

25, Beckhit, K, G,, and M, K. Hathout, 1966, Some factors affecting 

growth in suckling Friesian calves of an imported herd, Agric. 
Res, Rev., Cairo, ^iA(i-0:92. (cited in Animal Bdg. Abstr, I968, 
36:2420). 

26, Bereskin, B., and A. E. Freeman, I96I. Effect of month of 

calving fn herds at three levels of production, (Abst.) 
J. Dai ry Sci . , 44: 1 I96, 

27, Bereskin, B. , and A. E, Freeman, I965, Genetic and environ- 

mental factors in dairy sire evaluation. I, Effects of herds, 
months, and year-seasons on variance among lactation records; 
repeatability and herl tabi 1 i ty, J. Dairy Sci., 48:347, 

28, Bereskin, B. , and J. L, Lush, 1965- Genetic and environmental 

factors in dairy sire evaluation. III, Influence of environ- 
mental and other extraneous correlations among the daughters, 
J, Dai ry Sc i , , 48:356. 

29, Berge, S, 1946, Fertility and pregnancy percentage. (Abstr.) 

J. Dairy Sci, , 29:143. ■ 

.30, ,Bha!la, R, C. , D. P, S. Sengar, and B, K, Soni, I967. Study 

on the birth weight of Murrah buffalo and Sahiwal calves and 
factors affecting them. Indian J. Dairy Sci., 20:139. 

■31. Blackmore, D, W., L. D. McGilliard, and J. L. Lush. 1958, 

Genetic relations between body measurements at three ages 
in Holsteins, J, Dairy Sci,, 4l:1045. 

32. Bodisco, V,, E, Cevallos, and A, Carnevali, I966, Influencia de 

la estacfon climatica sobre la produccion de vacas criollas 
]echeras„ Mems. Assoc, Lat-Am. Prod, Anim., 1:141, 

33. Bodisco, v., E, Cevallos, A, Carnevali, and J. R. Gomez. I969, 

Four consecutive lactations in Criollo and Brown Swiss dairy 
cows in Maracay (Venezuela). Mems. Assoc, Lat-Am, Prod, 
Anim, ( i n press) , 

34. Bodisco, v., and G, Mazzari . I962. Eficiencia reproductiva de 

las vacas Criollas y Pardo Suizas en el Centro de i nves t i gaci ones 
Agronomicas, Ministerio de Agricultura y Cria, Centro de 
Investigaciones Agronomicas, Maracay, Venezuela, Bol. Tec. 
No. 14, 24 pp. 

35. Bodisco, v., C. E. Rios, F. Morillo, and A, Ocando, I962. 

Comportamiento del ganado criollo lechero en fincas privadas 
de la region del Rio Limon en el estado del Zulia, !, 
Informaciones pre 1 i mi nares , Ministerio de Agricultura y Cria. 
Bol. Tec. Mo. I3, 18 pp. 



» i ■ ? ■ #fM^ ■ ra i rt i*cj. 



36. 
37. 
38. 



39. 



40. 



41 



42. 



155 

Boletin Meteorologico. I966. Institute Col ombi ano Agropecuari o. 
No. 2, 22 pp. 

Boyazogul, J, G. I966, Production criteria of outstanding 
Friesland cows in South Africa. S. Afr. Friesld J,, 43:47. 

Boyazoglu, J, G. , H, J, Steenberg, J, H, Hofmeyer, and G. P, 

Kuhn. 1956, Preliminary notes on some production character- 
istics of elite Friesland cows in South Africa, Proc. S. Afr, 
Soc, Anim. Prod. , 5: 186. 

Boyd, L. J., D. M. Seath, and D. Olds. 1954, Relationship 
between level of milk production and breeding efficiency in 
dairy cattle, J. Animal Sci., 13:89, , 

Brakel, W, J., D. C. Rife, and S, M, Salisbury. I952. Factors 
associated with the duration of gestation in dairy cattle, 
J. Dairy Sci . , 35:179. 

Braude, R, , and 0. M, Walker, I949. Mortality, weight and 
body measurements at birth of dairy Shorthorn calves. J. 
Agr, Sci. , 39: I56, 

Briquet, R,, Jr., and J. De Abreu. 1949, The gestation period 
in Zebu breeds, I, The Guzerat, Publ. Inst, Zootec. (Rio 
de J,), No, 4:19. (cited in Animal Bdg, Abstr. I95I, 19:1676) 



43. Buch, N. C, W, J. Tyler, and L. E, Casida, I955, Post partum 

estrus and involution of the uterus in an experimental herd. 
of Holstein-Friesian cows. J, Dairy Sci., 38:73, 

44. Buch, N. C, W. J, Tyler, and L. E. Casida. I959. Variation in 

some factors affecting the length of calving intervals. J, 
Dairy Sci, , 42:298. 

45. Burdick, J. M, , and L, D. McGilliard. I963. Interaction between 

sires in artificial insemination and management of dairy 
herds. J. Dairy Sci,, 46:452. 



46. Burnside, E, B. , and J. C. Rennie, I96I. The heritability of 
milk yield at different levels of production and the effect 
of production differences on dairy sire appraisals, (Abstr.) 
J. Dairy Sci., 44:1 1 89 , 

Burris, M, J., and C, T, Blunn, 1952, Some factors affecting 
gestation length and birth weight of beef cattle, J, Animal 
Sci., 11:34. 

Carman, G. M, 1955. Interrelationships in milk production and 
breeding efficiency in dairy cows, J, Animal Sci,, 14:753. 



47. 



48. 



. s m^.mmMm f'j^r.rr- iiUh. 



156 

k3. Carrno, J. Do., and C. Batista. I96I, Estudo sobre o compor tamento 
da raca holandesa var, Malhada de Preto, na Fazenda Experi- 
metttal de Criacao "Santa Monica," Banco de Juparcana, Estado 
do Rio de Janeiro, Brasil. InstituLo de Zoo teen i a ( I , N, P, A.M.A, ) 
Boltein No. 29, 28 pp. 

50. Carmona, S., and H. Munoz. I966. Intervalo entre partes y 

numero de servicios por prenez en vacas criollas, Jersey y 
encastadas de Suizo en clima tropical humedo, Mems, Assoc. 
Lat-Am. Prod, Anim. , 1:7. 

51. Carneiro, G. , P. BrovjR, and S. M. Pompeu, 1957. Eficiencia 

reproductiva dasracas leiteiras europeias em Pedro Leopoldo. 
Arquivos da Escola Superior Veterinaria de U. R. E, M. G., 
1 : 25 . 

52. Carneiro, G. , and J. L. Lush. 195^1. Reproductive rate and 

growth of purebred Brown Swiss cattle in Brazil. J. Dairy 
Sci., 37:1U^5. 

53. Casida, L, E,, and W. G. Venzke, I936. Observations on 

reproductive processes in dairy cattle and their relation to 
breeding efficiency. Proc. Amer, Soc. Anim. Prod., pp 221, 

5^. Chapman, A, B. , and L. E, Casida. 1935, Length of service 

period in relation to productivity and reproductive efficiency 
in dairy cows. Proc, Amer. Soc, Anim, Prod., 66 pp. 

55- Chaudhuri, A, C, , and C, Sinha. 1951. Studies on gestation 
periods in Tharparkar cattle. Indian J. Vet, Sci., 21:6.9. 

56. Clapp, H, A, 1937- A factor in breeding efficiency of dairy 

cattle. Proc. Amer, Soc. Anim, Prod,, 259 PP. 

57. Clark, C. H. 1962, Effect of month of calving on the produc- 

tion of (Queensland dairy cows, Q,d . J, Agric, Sci., 19:267. 

58. Cooper, T, , D. Olds, and 0. W. Deaton. I967, Causes of varia- 

tion in calving intervals of dairy cattle, Progr, Rep, 
Kentucky Agric. Exp, Sta., 170:76. 

59. Copejand, L, 1930. Length of gestations in Jersey cows. J, 

Dairy Sci , , 13:257. 

60. Davis, H. P., M. Plum, and B. Brost. 195^. Studies of herd 

management records, II. Relation of gestation length to 
birth weight of Holsteln calves of both sexes at various 
calvings. J, Dairy Sci,, 37:162, 

61. Dawson, W, M, , R, W, Phillips, and W, H. Black. 19^7. Birth 

weight as a criterion of selection in beef cattle, J, 
Animal Sci . , 6: 2''i-7, 



6if. 



157 

62. De Alba, J., and C. Carrera, I958, Seleccion de ganado Criollo 

lechero tropica]. Com. de Turrialba No, 6I, 68 pp. 

63. Deaton, 0, W, , and L. D. McGilliard. ]96^K First, second, and 

third records of a cov-j to estimate superiority of her 
daughters. J. Dairy Sci,, ^tyrlOO^}, 

Deese, R. E, I965, A genetic evaluation of fertility and pre- 
weaning growth rate in Brahman and crossbred cattle. Ph.D. 
Dissertation, University of Florida, Gainesville. 

65. DeFries, J, C. , R, W. Touchberry, and R. L, Hays, 1959. 

Heritability of the length of the gestation period in dairy 
cattle. J, Dairy Sci., ^2:598. 

66. Dessouky, F, ! . , and A, H. Rakha. I96I. Studies on gestation 

period and post-partum heat of Friesian cattle in Egypt J 
Agrlc. Sci., 57:325. ' ' 

67. DHIA averages for centrally processed herds. I970. Dairy records 

processing center. North Carolina State University, Raleigh 
12 pp. 

68. Dicker-son, G. E. I96O. Techniques for research in quantitative 

animal genetics. Techniques and procedures in animal produc- 
tion research. American Society of Animal Science, 228 pp. 

69. Donald, H. P., W. S, Russel, and St, C. Taylor. I962. Birth 

weights of reciprocally cross-bred calves. J. Aqr Sci 
58:405. a ., 



70. 



Dunbar, R. S., Jr., and C. R. Henderson, 1953. Heritability of 
fertility in dairy cattle. J. Dairy Sci., 36:1063, 



71. During, T, 1937. Do the spermatozoa influence the duration of 

pregnancy in cattle? Z. Zuchtung, Reihe B, 39:25. (cited in 
Animal Bdg. Abstr. I938, 6:204). 

72. Eckles, C. H. 1918. A study of the birth weight of calves. 

Missouri Agr, Expt, Sta., Research Bull, 35, 

73. El-!triby, A. A., and A. A. Asker. I958. Some production 

characteristics of native cattle, Friesian, Shorthorn, and 
their crosses in Egypt. Empire J, of Exp. Agric, 26:314. 

74. E!~Sheikh, A. S., and M. A. El-Fouly. I962. Some factors 

affecting length of calving interval in a herd of Friesian 
cattle in the U.A.R. J, Anim. Prod. U„A.R. , 2:1. (cited in 
Animal Bdg, Abstr. I965, 33:3337). 

75. Erb, R.^E,, and A. 0. Shaw. 1948, Breeding failure survey in 

Washington, A summary. West Div, Am, Dairy Sci, Assoc. Proc. 
25 pp. 



- nf -■ •' :--n ■- ^-nrr — ri^n — 1 m~- t \mm -r » r'n'm^ i ■ mit m ii i n « ■ n r i'"ti. n n 1 iiiii _ '-^ — =— ' : ■— — 11 wi i h I i ii I imi ' ii w i 1 ■" Hij 



158 

76, Etgen, W, M, 1959. The effect of gestation on milk and butterfat 

production in dairy cattle. Diss. Abstr., 19:3071. 

77, Evans, ^D, L, , C, Branton, and B. R. Farthing, 196^. Heritabiiity 

estimates and interrelationships among production per day of 
productive life, longevity, breeding efficiency and type in a 
herd of Holstein cows, J, Dairy Sci,, ^7:699, 

78, Everett, R. W. , and W. T, Magee, I965, Maternal ability and 

genetic ability of birth weight and gestation length, J. 
Dai ry Sci , , ^8:957, 

79- Fallon, G, R, I958, Some aspects of oestrum in cattle, with 
reference to fertility on artificial insemination, 1, The 
pattern of oestrus cycles, Qd, J, Agric. Sci,, 15:25, 

80, Farthing, B,_R,, and J. R, Steele, I967. Biased estimates of 

heritabiiity resulting from incorrect methods of estimating 
components of variance. J. Dairy Sci,, 50:105, 

81. Fitch, J, B,, P, C. McGilliard, and G, M. Drumm, 1924, A study 

of the birth weight and gestation of dairy animals, J Dairy 
Sci. , 7:222, 

82, Foote, W, D,, W, J. Tyler, and L. E, Casida, 1959. Effect of 

some genetic and maternal environmental variations on birth 
weight and gestation length in Holstein cattle, J, Dairy Sci 
^^■2:305. 

83. Gacula, M. C, , Jr., S, N. Gaunt, and R. A, Damon, Jr, I968. 

Genetic and environmental parameters of milk constituents for 
five breeds. M, Some genetic parameters. J. Dairy Sci 
51:438. y ■> 



84. 



Gaines, W, L, I928, The energy basis of measuring yield in 
dairy cattle. iil. Agr, Expt. Sta., Bull. 308. 



85. Gravert, H, 0, I958. Untersuchungen uber die Heri tabi 1 i tat der 

Butterfettleistung, Z, Tierzucht, ZuchtBiol,, 71:155-163, 
(cited in Animal Bdg, Abstr, I958, 26:1878). 

86. Gravert, H. 0, I959, Zur Bewertung der Mi 1 chfett 1 e i s tung in 

absoluten oder prozent i schen Zahlen. Zuchtungskunde , 31: 
345--349. (cited in Animal Bdg. Abstr, !96l, 29:752). 

87. Grossman, J., and W, M. De Oliveira, 1949- Factors influencing 

gestation period and birth weight in dairy breeds. Bol, Dir. 
Prod. Anim., 5(7), 11:19, (cited in Animal Bdg. Abstr. '1950* 
18:1380), ^ ' 



88. 



Gur" Yanava, A, S, I967, Variation, heritabiiity and relationship 
to milk yield of fat and protein contents of milk of Latvian 
Red cows and Jersey crosses. Dairy Sci. Abstr., 30, No. 2932, 






159 

89. Herman, H, A,, and J, H, Edmondson. 1950, Factors affecting the 

interval between parturition and first estrus in dairy cattle. 
Mo. Agr. Expt, Sta., Res, Bull, if62, 

90. Herman, H, A,, and R, V! . Spalding. 19^7. A study oF factors 

affecting length of gestation in dairy cattle, J, Dairy Sci . , 
30:5^6. 

91. Herman, H, A,, R, W, Spalding, and K. W, Bower, 1953. Factors 

affecting length of gestation in dairy cattle, Missouri Agr, 
Expt. Sta,, Research Bull, 529. 

92. Hickman, C. G,, and C, R, Henderson. 1955, Components of the 

relationship between level of production and rate of maturity 
in dairy cattle. J, Dairy Sci,, 38:883, 

93. Hirsch, S,, and H. Schindler, I957, The Syrian and Dutch 

Friesian cattle, and their crosses in Israel. Ktavin, Rec, 
Agric. Res. Sta. ,7:2, 

3k. Hirt, R. 1953. Gestation period and service period in German 

Spotted Mountain cattle in North Baden. Dissertation, Vet.- . 
Med. Fak. , Jus tus-l.i ebi g-Hochsch, , Giessen, k] pp. (cited 
in Animal Bdg. Abstr, I955, 23:636), 

95- Hofmeyer, J, H, , and J, G. Boyazoglu. 1962, Notes on a few 
phenotypic and genetic parameters of Friesland and Jersey 
cattle in South Africa, Proc, 2nd Congr, S. Afr. Genet, Soc. , 
1962, (cited in Animal Bdg, Abstr. I96U, 32:l880), 

96, Jafar, S. M, , A, B. Chapman, and L. E. Casida. I95O, Causes of 
variation in length of gestation in dairy cattle, J. Animal 
Sci., 9:593. 



97. Johansson, !. I95O. The heritability of milk and butterfat 

yield. Animal Bdg. Abstr,, 18:1. 

98. Johansson, !, 1953. The manifestation and heritability of 

quantitative characters in dairy cattle under different 
environmental conditions. Acta genet., i|:221. (cited in 
Animal Bdg. Abstr. I954, 22:523). 

99- Johansson, I, I96I. Genetic Aspects of Dairy Cattle Breeding. 
University of Illinois Press. Urbana. 

100. Johansson, 1,, and J. Rendel, I968. Genetics and Animal 

Breeding, W, H. Freemian and Company. San Francisco. 

101, Johar, !<, S. , and C= M. Taylor. I967. Calving interval in 

Sahiwal and Red Sindhi cows. JNKVV Res. J,, 1:^4, (cited in 
Animal Bdg. Abstr. I968, 36:305). 



160 

102. Johnson, A, D,, R, F. Behlow, M. E. Senger, and L. C. Ulberg, 

1966, Evaluating reproductive status and its influence in 
dairy herds, J, Dairy Sci,, kS-J\-S]. 

103. Jordao, L. P., and F, De Paula Assis. 1951, Pvcproduct i ve 

efficiency, birth weight and growth in Mense--Pxh i ne-Ysse 1 
cattle. Bol industr. Anim., M.S., 12:^5, (cited in Animal 
Bdg, Abstr, I952, 20:1586), 

]Gk. Jordao, L, P, , and J, S. Veiga, 1938. Estudo sobre a duracao do 
periodo de gestacao no gado caracu. Rev. Ind. Animal, N.S,, 
I ■< 



105. Joubert, D. M, 1955. The influence of high and low nutritional 

planes on the oestrus cycle and conception rate of heifers. 
J. Agric. Scl . , 45:164. 

106. Joubert, D, M. , and J, C, Bonsma, 1959. Gestation of cattle In 

the sub-tropics, with special reference to the birth weight 
of calves. S, Afr. J, Agric, Sci., 2:215. 

107. Juma, K, H. , and S, M, Kassir. I967. Some factors influencing 

birth vjeights of pure-bred and crossbred Friesian calves. 
Indian J, Dairy Sci,, 20:19, (cited in Animal Bdg, Abstr. 
1968, 36:2516). 

108. Klein, J. W, , and T, E, V/oodward. 19^3, influence of length of 

dry period upon the quantity of milk produced in the subsequent 
lactation, J, Dairy Sci., 26:705. 

109. Knott, J. C. 1932. A study of the gestation period of Holstein- 

Friesian cows, J. Dairy Sci., 15:87. 

110. Koch, R, M, , and R. T, Clark, 1955- Genetic and environmental 

relationship among economic characters in beef cattle, I. 
Correlation among paternal half-sibs. II, Correlations 
between offspring and dam and offspring and sire. J, Animal 
Sci., 1:775. 

111. Kohli, M. L., and K, R. Suri. I957. Factors affecting birth 

weight in Hariana cattle, Indian J. Vet. Sci., 27:33. 

112. Korman, N. 1953. Versuch einer verglei chenden Nachkommenschaf t- 

suntersuchung von Bullen, die in h'erden mi t verschieden 
starker Futterung wirken, Z, Tierzucht, Zucht Biol., GI: 
375-390. (cited in Animal Bdg, Abstr. 1953, 21:1675). 

113. Kushwaha, N, S, 1964, Heritability and repeatability of 

calving interval in Sahiwal dairy cattle, Kanpur Agric. Coll. 
J,, 24:23. (cited in Animal Bdg. Abstr. I966, 34:1135). 

114. Lasley, J, F. , and R. Bogart. 1943. Some factors influencing 

reproductive efficiency of range cattle under artificial 
and natural breeding conditions. Missouri Agric. Exp, Sta., 
Bull, 376. 



161 

115. Lazarus, A, J,, and C, P, Anantaki shnan. 1952. Observations 

on some Indian cattle. Part !. The period of gestation in 
cows, Indian J, Dairy Sci,, 5:9. 

116. Legates, J, E, 195^- Genetic variation in services per con- 

ception and calving interval in dairy cattle, J. Animal 
Sci., 13:81. 

117. Legates, J, E,, F. S. Verlinden, and J. F. Kendrick, I956. 

Sire by herd interaction in production traits in dairy 
cattle. J. Dairy Sci,, 39:1055. 

118. Legault, C, R., and R. W, Touchberry, I962, Heritability of 

birth weight and its relationship with production in dairy 
cattle, J, Dairy Sci,, i+5:1226. 

119. Lush, J. L. , and R. R. Shrode. I95O. Changes In milk produc- 

tion with age and milking frequency, J. Dairy Sci., 33:338. 



120, 



Lytton, V. H, , and J, E, Legates. I966, Sire by region inter- 
action for production traits in dairy cattle. J. Dairy Sci 
49:874. 



121, Magofke, J. C, andV, Bodisco. 1966. Estimaclon del mejoramiento 

genetico del ganado criollo lechero en Maracay, Venezuela, 
entre los anos l955--6i:-. Mems . Asoc, Lat-Am. Prod. Anim., 
1:105. 

122, Magofl<e, J, C, J. De Alba, and H, Munoz, I966, Informe del 

progreso sobre mejoramiento genetico del ganado criollo 
lechero en Turrialba, Mems, Asoc. Lat-Am. Prod. Anim 
1:77. 

123, Mahadevan, P. I953, The general life and production statistics 

of the Sinhala cattle of Ceylon, Empire J. of Exp. Agric. 
21:55. 

124, Mahadevan, P. I954. Repeatability and heritability of milk 

yield In crosses between Indian and European breeds of dairy 
cattle, Emp. J, Exp. Agric, 22:93, 

125, Mahadevan, P. 1956. Variation in performance of European dairy 

cattle in Ceylon. J, Agric. Sci., 48:164. 

126, Mahadevan, P, I966, Breeding for Milk Production in Tropical 

Cattle, Commonwealth Agricultural Bureaux, Farnham Royal, 
Bucks, England, 

127, Mahadevan, P., and H, G. Hutchison. 1964, The performance of 

crosses of Bos taurus and Bos indlcus cattle for milk 
production In the coastal region of Tanganiyka. Animal Prod,, 
6:331. 



162 

128. Mahadevan, P., and H. J, S, Marples, I96J , An analysis of the 

Entebbe herd of Nganda cattle in Uganda. Animal Prod., 3:29, 

129. Maksla, A,, and R, Oittila. 1355. Gestation period of Ayshire 

cows at the Viik experimental farm, Maataloust. Aikakausk, , 
27:77, (cited In Animal Bdg. Abstr, I956, 2h:]k]). 

130. Mao, I, L,, and E, B. Burnside, I969. Sire by herd environ- 

ment Interaction for milk production, J, Dairy Sci,, 52:1055, 

131. Marples, H, J. S,, and J, C, M, Trail, I966. An analysis of 

a commercial herd of dairy cattle In Uganda, Trop. Agr. , 
(Trinidad) Vi:69, 

132. Martin, T. G, 1956, Factors affecting growth rate of dairy 

calves, Iowa State Coll, J, Sci., 30:^12, 

133. Mason, I, L, , and A. Robertson. The progeny testing of dairy 

bulls at different levels of production, J, Agric, Sci., 
^7:367. 

13^. McCandlish, A, C, 1922, Studies In the growth and nutrition 
of dairy calves. J, Dairy Sci,, 5:301. 

135. McDaniel, B, T. , and E, L. Corley, I967, Relationships between 

sire evaluations at different herdmate levels. . J, Dairy Sci,, 
50:735. 

136. Mies Filho, A., and J, A, D. Costa Aroeira, 1955, The interval 

between calving and post-partum oestrus in the Zebu dairy 
cattle of Uberaba, Bol, I nsem.- Art] f , (Rio de J.), 7:11, 
(cited in Animal Bdg, Abstr, I957, 25:1825), 

137. Morrow, D, A., S, J. Roberts, K. McEntee, and H, G. Gray, I966, 

Post-partum ovarian activity and uterine involution in dairy 
cattle. J, Am. Vet. Med, Assc. , 1^9:1596. 

138. Naidu, K. N. , and R, N. Desai, I966, Genetic studies on 

Hoi stei n-FrlesIan x Sahiwal cattle for their suitability in 
Indian tropical conditions as dairy animals. ML Productive 
characters, Indian J. Vet, Sci., 36:61. 

139. Nalbandov, A, V, 1953, Reproductive Physiology. W, H. Freeman 

and Co. San Francisco, 

lifO. Narvaez Ramirez, G. L, I95I. Production from Jersey and 
Holstein breeds In a humid tropical climate and under 
intensive management. Turrialba, 1:28^, 

1^1, Naufel, F. 1966, Effects of some environmental and genetic 
factors on milk and butterfat yield in an experimental 
Hoi stei n-Frlesian herd in the Department of Animal Production 
at Sao Paulo, Bolm Ind, Anim,, N.S,, 23 (1965):21. (cited 
in Animial Bdg. Abstr. I97O, 38:1306.) 



163 

1^2, Norman, H, D, , and H. W, Thoele. I967. Effects of calving 
interval upon 305-clay milk and fat production. (Abst.) 
J. Dairy Sci. , 50:4?. 

143. O'Bleness, G. V., and L. D. Van VIeck. 1962. Reasons for 
disposal of dairy cows from New York herds. J, Dairy Sci 
45:1087. 



\kk. 



Olds, D,, H, B. Morrison, and D. M. Seath, I9V,. Efficiency 
of natural breeding in dairy cattle, Kentucky Agr. Expt, 
Sta. , Bui 1. 539. 



\k5. Olds, D., and D. M. Seath. 1953- Repeatability, he ri tab i 1 i ty , 
and the effect of level of milk production on the occurrence 
of first estrus after calving in dairy cattle, J, Animal 
Sci., 12:10. 

146. Okumu, C, and J. C, Berry. I966. Studies of milk production 

in crossbred dairy cattle-. E, Afr, Agric, For. J., 32:163. 

147. Parker, J. B., N. D. Bayley, M. H, Fohrman, and R. D, Plowmian. 

i960. Factors influencing dairy cattle longevity. J. Dairy 
Sci. , 43:40! . 

148. Pearson, L. , R, K. Waugh, B, Salazar, F. M. Botero, and 0. 

Acosta. 1968, Milking performance of Blanco Oreji negro 
and Jersey cross-bred cattle. J. Agr. Sci., 70:65. 

149. Plum, M. 1935. Causes of differences in butterfat production 

of cows in Iowa testing associations. J. Dairy Sci., 18:811. 

150. Plum, M., H. Andersen, and L, A. Swiger. I965. Heritability 

estimates of gestation length and birth weight in Holstein- 
Friesian cattle and their use in selection indexes. J. 
Dairy Sci. , 48:1672. 

151. Plum, M, , and J. L, Lush. 1934. Freshening ages of purebred 

cows in Iowa cow testing associations, J, Dairy Sci., 17:625. 

152. Poston, H. A., L. C, Ulberg, and J. E. Legates. I962. Analysis 

of seasonal fluctuations of reproductive performance in 
dairy cows, J, Dairy Sci,, 45:1376. 

153. Pou, J. W,, C. R. Henderson, S. A. Asdell, J, F. Sykes, and R, 

C. Jones. 1953. A study of the inheritance of breeding 
efficiency in the Beltsville dairy herd. J. Dairy Sci., 36: 
909. 

154. Ragab, M. T. , and A. A. Asker. I95I. Factors influencing 

length of gestation period in Egyptian cattle and buffaloes. 
Indian J. Dairy Sci., 4:159. 



164 

155. Ragab, M, T, , and A, A, Asker, I96I, Some economic character- 

istics of the Friesian cattle in the Tahreer Province, Ann. 
Agric. Sci. (Cairo), h. No. 1 (I959:!07. (cited in Animal 
Bdg, Abstr. 1963, 31 :146), 

156. Rendel, J, 1959. Factors influencing gestation length in 

Swedish breeds of cattle. F, Tierz, Zucht Biol., 73:117. 
(cited in Animal Bdg, Abstr. I960, 28:1886), 

157. Rendel, J. J968, The productivity of indigenous and temperate 

dairy cattle and their crosses in tropical climates. Food 
and Agriculture Organization of the United Nations, (FAG) AN: 
AGR/68/5. 

158. Rice, V, A., F. N. Andrews, E. J, Warwick, and J. E. Legates, 

1967. Breeding and Improvement of Farm Animals, 6th edition, 
New York, McGraw-Hi 1 1 , 

159. Rios, C. E,, and V. Bodisco. I962, Estado actual de los 

estudios del ganado lechero en el Centro de I nvesti gaciones 
Agronomicas. Ministerio de Agriculture y Cria. Centro de 
1 nvestigaciones Agronomicas, Maracay, Venezuela Bol Tec 

No. n , 13 pp. ' 

160. Robertson, A. I950, A preliminary report on the herd of 

Fulani cattle at Shika, Nigeria. Conference on the improve- 
ment of Livestock under Tropical Conditions, Dec, 1950, 
Edinburgh, Scotland, 5 pp. (Mi m,eograph) , 

161. Robertson, A., L. K, O'Connor, and J. Edwards. I96O. Progeny 

testing dairy bulls at different management levels. Anfmal 
Prod., 2:141. 

162. Rollins, W. C, R. C. Laben, and S. W. Mead, I956, Gestation 

length in an inbred Jersey herd, J. Dairy Sci., 39:1578. 

163- Roman, J., C. J. Wilcox, and F. G, Martin. 1970. Milk produc- 
tion of tested Holsteins inEcuador. (Abst.) J. Dairy Sci 
53:673. 



164. 



Roman, J,, C, J, Wilcox, F. G. Martin, R, B. Becker and M. Koger. 
1970.. Maternal effects on birth weights of Jersey calves. 
(Abst.) J. Dairy Sci,, 53:655. 



165. Roy, N. C, and S. K. Goswami. I96O, Variations in the birth 
weight of Zebu x Friesian crossbred cattle. Indian Vet. J., 
37:409. 



166. 



Rubio, R,, and J. J, Salazar. 1966. Curso de pastes y ganaderia. 
Centro Nacional de I nvesti gaci ones Agropecuari as "Turipana." 
SCA, Publicacion de] Centro de Comuni caci ones. 



167. Salazar, J. J, I965. Relationship between age at first 

calving and lifetime production. Unpublished M.S. thesis. 
North Carolina State University. 



165 

168. Salisbury, G, V/. , and N. L, VanDeniark. I96I. Physiology of 

Reproduction and Artificial insemination of Cattle. W, H, 
Freeman and Company. San Francisco, 

169. Sanders, H. G. I928, The variation in milk yield caused by 

season of the year, service, age, and dry period, and their 
elimination. J, Agr, Sci,, 18:46, 

170. Saxena, P. N, , and S. Kumar. I96O, Persistency of milk yield 

in Sahiwal cows, Indian J, Dairy Sci,, 13:45, 

171. Seath, D. M. ig'iO, The intensity and kind of selection actually 

practiced in dairy herds. J, Dairy Sci., 23:931, 

172. Sharda, D. P., V, K. Bhatnagar, and K, L. Lohia. I967. Effect 

of month and sequence of calving on milk yield and calving 
interval in Mariana cattle. J. Res, Punjab Agric. Univ., 
4:575. (cited in Animal Bdg, Abstr, 1968, 36:3446), 

173. Singh, 0, N, 1961, Genetic study of natural services per 

conception in dairy cattle. Indian J. Vet, Sci,, 31:310, 

174. Singh, S, B., and R. N. Desai. I96I , Inheritance of some 

economic characters in Mariana cattle. Ml. Milk yield, 
Indian J, Dairy Sci,, I4:l4l. 

175. Singh, S. B., and M, Dutt. I963. Effect of season of calving 

on milk production, lactation period and service period In 
Sahiwal cattle, Indian Vet, J., 40:362, 

176. Singh, R, M, , and R. B, Prasad, 1968. Genetic and phenotypic 

study of calving interval of Mariana cattle in Bihar. Indian 
Vet. J, , 45:407, 

177. Singh, 0. N, , B, D, Sinha, and B. P. S, R. Singh. I958. Environ- 

mental and hereditary causes of variation in length of gestation 
of Tharparkar cows, Indian J, Dairy Sci,, 11:109, 

178. Smith, J. V/. , and J. E, Legates. I962, Relation of days open 

and days dry to lactation milk and fat yields. J. Dairy 
Sci. 45:1192. 

179. Seller, M,, G. Bonsall, and H. Angel, 1964. Heritability and 

repeatability of five iTieasures of milk production in Israel 
Friesian dairy herds. Israel J, Agric. Res., 14:111, (cited 
in Animal Bdg, Abstr, I965, 33:1125). 

ISO. Spalding, R. W, I962, Some effects of service period and dry 
period on milk and butterfat production. Diss. Abstr., 
22:3794. 

181. Stallcup, 0. T. , 0. H. Morton, and C. J. Brown. I956. The 

duration of gestation in dairy cattle. Arkansas Agr. Expt. 
Sta. Bull. 576. 



166 

-182. Stone, E, J., E, G, Morgan, J. E, Johnston, and J, B. Frye, Jr. 
1958. A preliminary analysis: Birthweights of Holstein 
and Jersey female calves born in Southern Louisiana. J. 
Dai ry Sci . , k] :3^3. 

183'. Swanson, E, W, 1961, Milk production and growth of identical 
twin heifers calving for the first time at two and three 
years of age. J. Dairy Sci., ^-^iZOZy, 

iB^f. Swiger, L. A., W, R. Harvey, D, 0, Everson, and K, E, Gregory. 
196^. The variance of intraclass correlation involving 
groups -with one observation. Biometrics 20:818, 

185. TabTer, K, A,, and R. W. Touchberry. I955, Selection indices 

based on milk and fat yield, fat percent and type classifica- 
tion. J, Dairy Sci, , 38:1155. 

186. Tabler, K. A., W. J. Tyler, and G. Hyatt, Jr. I95I. Type, 

body size, and breeding efficiency of Ayrshire cow families. 
J. Dairy Sci, , 3^n95. 

187. Tanabe, T. , and G. V/, Salisbury, 19^1-6, The influence of age 

on breeding efficiency of dairy cattle in artificial 
insemination, J. Dairy Sci,, 29:337. 

188. Taylor, J, C, R, C. Carter, C. M, Kincaid, B, M, Priode, and 

J. A, Gaines. igSO. Estimates of genetic and phenotypic 
parameters in beef cattle, iV. Repeatability of cow 
performance, J. Animal Sci,, 19:700, 

189. Touchberry, R, W, , K, Rottensten, and H, Andersen, I96O, A 

comparison of dairy sire progeny tests mads at special 
Danish testing stations with tests made in farm herds. J, 
Dai ry Sci , , 43:529, 

190. Towles, R. C. 1918. The relation of milk yield to age at first 

calving. Mo. Agr. Expt, Sta,, Bull, 217, 

191. Trimberger, G, W. , and P, H, Davis. 19^5. Predictability of 

breeding efficiency in dairy cattle from their previous 
conception rate and from their heredity, J. Dairy Sci 
28:659. 

192. Tyler, W. J., A, B, Chapman, and G, E, Dickerson, 19'^7, Sources 

of variation in the birth weight of Hoi stei n-Fr iesi an calves. 
J. Dairy Sci, , 30:483. 

193. United States Department of Agriculture. I962. Dairy statistics 

through I96O, Economic Research Service, Statistical Bull. 
303, Washington, D, C. 

194. VanDemark, M. L. , and G. W. Salisbury. I95O. The relation of 

the post-partum breeding interval to reproductive efficiency 
in the dairy cow. J. Animal Sci., 9:307, 



167 



195. Van Vleck, L, D. 1963- Genotype and environment in sire 
evaluation, J. Dairy Sci . , 46:983,, 



196, Van VIeck, L. D., and G. E. Bradford. 1964, Heritability of milk 

yield at different environmental levels, Anim. Prod,, 6:285, 

197. Van VIeck, L. D, , L. H. Wade 11 , and C, R. Henderson. I96I. Compo- 

nents of variance associated with milk and fat records of arti- 
ficially sired Holstein daughters, J, Animal Sci,, 20:812. 

198, Veiga, J. S,, 0. M, Pa i va , and A. Chieffl. I947. Study of the 

duration of the gestation period in Friesian cows. Boi . 
Industr. Anim,, N.S., 9:32. (cited in Animal Bdg, Abstr, 
1948, 16:1374). 

199. Verde, 0. G, I969. Factors affecting milk production in three 

Venezuelan herds, M, S, thesis. University of Florida, 
Ga i nesvi 1 1 e, 

200, Vukavic, D. 1952, The gestation period of Simmenta! cattle, 

Pojjopr. Znanst, Smot. (Zagreb), 13:85. (cited in Animal Bdg, 
Abstr. 1954, 22:129). 

201. Wade]], L, H, , and L, D, McGilliard. ]35:> . Influence of 

artificial breeding on production in Michigan dairy herds. 
J. Dairy Sci. , 42:1079. 



202, 



Ward, A, H. , and 0, M, Castle, 1948, Average length of 
gestation period in diary cattle in New Zealand. N.Z.J. 
Sci , Tech, , 29: 17] , 



203. Wells, M, fc,, D. G. V/agner, G, L, Holland, B, Stringer, and T, 

Wondafrash, 1969. Dairy cattle breeding and production re- 
search in Ethiopia, (Abst.) J, Dairy Sci,, 52:925, 

204. Wheat, J, D,, and J. K, Riggs. 1958. Her i tabi 1 i ty and repeatability 

of gestation length in beef cattle. J, Animal Sci., 17:249, 

205. White, J. M, , and J. R, Nichols. I965. Relationships between 

first lactation, later performance, and length of herd life in 
Hol stefn-Friesian cattle, J. Dairy Sci,, 48:468, 

206. Wilcox, C. J., K, 0. Pfau, and J. W. Bartlett. 1957. An 

investigation of the inheritance of female reproductive 
performance and longevity, and their interrelationships 
within a Hoi s tei n-Fr i esi an herd, J. Dairy Sci., 40:942. 

207. Wilcox, C. J., and D. K. Roy, I968, Factors affecting birth 

weights and gestation lengths in Jersey cattle, (Abst.). 
J, Dairy Sci, , 51:629, 



168 

208, Wilcox, C. J., and J, A. Staffa, 1964. Effects of uterine 

horn pregnant, age of dam and sex of calf on birth weights 
and gestation lengths of dairy cattle, (Abst,), J, Dairy 
Sci, , 47:346. 

209, Wilcox, C. J,, and H. W. Young. 1962, Effect of season and 

year of freshening on milk production. Fla, Agr, Exp, Sta,, 
Dairy Science Mimeo Report 63-3. 

210, Woodward, T. E, 1945, Some studies of lactation records, J. 

Dai ry Sci , , 28:209. 



BiOGRAPHiCAL SKETCH 

Juan Jose Salazar C. was born in Anserma (Caldas), Colombia, on 
March ih , ]g35. in November, 1953, he was graduated from San 
Bartolome (La Merced) High School at Bogota, Colombia. In December, 
195^-, he attained the rank of reserve lieutenant from the School of 
Infantry in Bogota, in I96I, he received the degree of Bachelor of 
Veterinary Medicine and Animal Husbandry from the National University 
at Bogota. In his senior year he was elected student president of 
his college. In this capacity he served as representative of the 
Veterinary Medicine School on the National University Student Body 
from i960 to 1961 , 

Following graduation, he enrolled as Animal Science researcher 
in the National Dairy Program at the Colombian Agricultural institute 
in Bogota. 

fn September, I963, he entered Graduate School at North Carolina 
State University. In 1966 he was granted the degree of Master of 
Science, in September, 1967, he enrolled at the University of Florida 
and has been working towards the degree of Doctor of Philosophy, 

He is a member of the Colombian Society of Veterinary Medicine; 
he is also a charter member and was first president of the Colombian 
Association of Animal Production. At the present time he belongs to 
the Board of Directors of the Latin Am.erican Association of Animal 
Production. He is also a member of the American Dairy Science 



169 



170 
Association, and the American Society of Animal Science, While attend- 
ing the University of Florida, he was elected to membership in the 
Gamma Sigma Delta and Sigma Xi societies. 

He is married to the former Lucy Munoz and is the father of one 
child. 



This dissertation was prepared under the direction of the 
chairman of the candidate's supervisory committee and has been 
approved by a]] members of that committee. It was submitted to the 
Dean of the College of Agriculture and to the Graduate Council, and 
was approved as partial fulfillment of the requirements for the 
degree of Doctor of Philosophy. 



June, 1970 



-Ci^^l^C 



Dean, College of T^ri cul ture 



Dean, Graduate School 



Supervisory Committee; 



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0' 




Chai rman 






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